A HISTORY OF SCIENCE 



even by the most tender-hearted anti-vivisectionist, 

 for availing himself freely of material which otherwise 

 would probably serve no better purpose than to ap- 

 pease the appetite of some rapacious fish. 



Their abundance is not the only merit, however, of 

 the eggs of pelagic creatures, in the eyes of the biologist. 

 By equal good-fortune it chances that colorless things 

 are at a premium in the sea, since to escape the eye of 

 your enemy is a prime consideration. So the eggs in 

 question are usually transparent, and thus, shielded 

 from the vision of marine enemies, are beautifully 

 adapted for the observation of the biologist. As a final 

 merit, they are mostly of convenient size for manip- 

 ulation under the microscope. For many reasons, then, 

 the marine egg offers incomparable advantages to the 

 student of cell life, an egg being the typical cell. And 

 since nowadays the cell is the very focus of attention 

 in the biological world, the importance of marine 

 laboratories has been enhanced proportionately. 



But of course not all the work can be done with eggs 

 or with living specimens of any kind. It is equally 

 important on occasion to examine the tissues of adult 

 specimens, and for this, as a rule, the tissues must first 

 be subjected to some preserving and hardening proc- 

 ess preliminary to the cutting of sections for micro- 

 scopical examination. This is done simply enough in 

 the case of some organisms, but there is a large class of 

 filmy, tenuous, fragile creatures in the sea population 

 of which the jellyfish may be mentioned as familiar 

 examples. Such creatures, when treated in an ordinary 

 way, by dropping them into alcohol, shrivel up, coming 

 to resemble nothing in particular, and ceasing to have 



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