Pale and ghostlike, they float gently inside their womb of shining glass. Each has the snout, feet and prickly coat of a hedgehog, yet none is quite ready for the rough and tumble of woodland life. They are just three of the thousands of embryos collected in the late 19th century by Ambrosius Hubrecht, a gentleman scientist from the Dutch city of Utrecht. Today, behind a heavy fireproof door at the Hubrecht Laboratory in Utrecht, there are rows of wooden cabinets crammed with bottles and jars containing mammals at every stage of development, from fertilised egg to the newborn. Miniature moles suspended in spirit share a shelf with sharp-snouted shrews collected each summer in the nearby countryside. From farther afield came tree shrews, lemurs and tarsiers. Hubrecht鈥檚 glass menagerie conjures up a time when collecting was an adventure and an end in itself. Look inside the jars and it鈥檚 easy to imagine the wealthy young biologist, leading his hunting parties into the jungles of Sumatra and Borneo with local tribesmen as research assistants and guns as collecting tools.
AMBROSIUS HUBRECHT was taking his evening stroll through the woods of Beukenburg, a few kilometres from Utrecht, when he stumbled across two men rummaging about in the undergrowth. What, he asked, were they looking for? Hedgehogs, said one, pointing to the bulging sack on his back. 鈥淪ome crazy man in Utrecht is willing to pay 25 cents for each living hedgehog.鈥� Hubrecht went on his way, later jotting down the conversation in his diary. The hedgehog hunters hadn鈥檛 guessed, but they鈥檇 just met their crazy man.
Hubrecht, a young professor at the University of Utrecht, was interested in embryology and the mammalian placenta in particular. He wanted to understand how the placenta develops during pregnancy, and how mammals had acquired it.
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Insectivores seemed the best place to start, on the grounds that they were not much different from the first placental mammals. And of all the different insectivores, hedgehogs and malodorous, hairy gymnures were considered the nearest thing to the original model.
Unfortunately, the hedgehogs proved uncooperative. They refused to breed in captivity, upsetting Hubrecht鈥檚 plans to sample embryos at every stage of development. But the ambitious young professor came from a wealthy banking family. He placed a 鈥渉edgehogs wanted鈥� advertisement in the local paper offering the vast sum of 25 cents a hedgehog-and waited.
For the next few years, the summer months saw half the population of Utrecht out scouring the countryside for hedgehogs. Word spread and with a good haul of hedgehogs worth a week鈥檚 wages, people were soon travelling a hundred kilometres or more to bring him specimens. Eventually Hubrecht had enough pregnant animals to trace development from fertilised egg to birth. And in the leisurely manner of the Victorian scientist, Hubrecht carefully prepared hundreds of microscope slides and drew what he saw in meticulous detail.
After hedgehogs came moles and shrews, collected in cigar boxes at harvest time. But Europe鈥檚 poor assortment of insectivores were not enough to satisfy Hubrecht鈥檚 curiosity. He began to look elsewhere-to the Dutch East Indies (now Indonesia), South Africa and Madagascar.
Hubrecht did things in style, financing hunting parties to build up his collection. Instead of tigers or rhinos, his trophies were smaller beasts. He wanted more species of insectivores to see how they varied. He also added lemurs and lorises to his list because he hoped these primitive primates might tell him something about the nature of human development.
Sometimes he went himself, sometimes he sent a shopping list of animals and detailed instructions on how collectors should remove and preserve the embryos. He offered 50 cents a specimen regardless of the country, the species or even the sex.
One expedition was especially successful. In 1889, the Royal Physical Society in Batavia (the Javan capital, now known as Jakarta) invited Hubrecht to explore the islands of Indonesia, a chance he jumped at. He tried to identify the best collecting places before he set out by sending ahead coloured drawings of animals he wanted.
Even so, Hubrecht realised that he couldn鈥檛 possibly collect all the specimens he needed so he spent much of his time building up a network of contacts who might carry on collecting after he left. 鈥淚 left behind me printed instructions, chemicals, glass tubes, etc., as well as cash for the payment of premiums to the natives by whom the collecting of the live material was to be done,鈥� he wrote. If they ran out of alcohol, he suggested that they fill their bottles with arak, the native spirit distilled from rice.
There were some problems even Hubrecht couldn鈥檛 foresee. In East Java, no one would sell him a slow loris. Local lore had it that burying a loris skeleton in your enemy鈥檚 garden would bring destruction on his house. 鈥淚t is thus in high demand among the wealthier natives who have family quarrels to settle, and I have known exorbitant prices, with which a collecting embryologist could not possibly compete . . .鈥�
After returning to Utrecht, Hubrecht was pleasantly surprised when his colonial collectors continued to send him batches of specimens. After three years, he had more than a thousand exotic embryos.
Hubrecht quietly got on with observing and drawing, always looking for differences between the embryos that might be used to refine the mammalian family tree. He coined the word 鈥渢rophoblast鈥� to describe the outer layer of embryo cells that grows into the placenta, and founded an international society for the study of embryology. More important perhaps, before he died in 1915 he made sure there was money to preserve his collection.
Today, Hubrecht鈥檚 vast assortment of species offers an opportunity to answer some important questions about the evolution of embryos. According to evolutionary biologists, mammalian embryos all start the same-their form controlled by identical genes. Later, other genes come into play, giving each species its distinctive look.
But there is now a new school of thought that says even the earliest embryos are subject to evolution. The genes that control development vary subtly from one mammal to another right from the start. The challenge is to find little anatomical differences between embryos that would match those subtle molecular differences. And where better to look for them than among Hubrecht鈥檚 brilliant creatures?