54 



THE MUSEUM. 



titute of nourishing substances that it 

 can suffice for the needs of the devel- 

 opment for but a few hours. 



It may be destitue of any envelope 

 beyond a thin structureless membrane 

 formed by the egg-cell itself, or it may 

 be closely wrapped up in a series of 

 coverings, and outside of these we may 

 find a shell or case of complex form 

 and architecture. 



The eggs of animals are, indeed, 

 endless in variety, when the size, 

 amount of food-yolk, coverings and 

 appendages and the modes in which 

 they are deposited are taken account 

 of. But with all this one fact stands 

 out very clearly, that the size, compo- 

 sition, mode of deposition, etc., of any 

 particular egg, have an intimate rela- 

 tion and connection with the develop- 

 ment of an individual of the species 

 whose egg it is. 



The individual peculiarities of ova 

 raise various interesting questions which 

 have hither to received out the barest 

 consideration in embryological text- 

 books and even in developmental re- 

 searches. Probably for solutions of 

 most of them the science will have 

 long to wait. The nature of most 

 modern embryological research is, un- 

 fortunately, not such as to furnish 

 hints in the direction of their elucida- 

 tion; the amount one man can accom- 

 plish, even if he be conscious of the 

 existence and importance of the prob- 

 lems, is but the merest trifle, and his 

 labors will require an enormous com- 

 parative material, if the results were 

 to be of far reaching import. 



These reasons, paradoxal though it 

 may seem to be, impel the writer to 

 attempt some sort of consideration of 

 the subject. It might be made the work 

 of a lifetime without evidence of ex- 

 haustion of the subject. If we are ever 

 to have a true and real comparative em- 

 bryology of organisms, as well as the 

 existing comparative embryology of 

 organs, many questions relating to 

 the eggs of animals, will need to be 

 cleared up. 



Facts are to be found for the seek- 



ing; but as every conscientious embry- 

 ologist realizes, the search nowadays, 

 especially if it be in some definite di- 

 rection, is often long and arduous. 

 And the result often may be a single 

 fact and a dozen new problems. More- 

 over, most of us have our plans of 

 work mapped out for years to come, 

 and have no desire to forsake the plot 

 of ground which we have diligently and 

 hopefully tilled, before we have reaped 

 our little harvest. Therefore, since 

 the problem of the individuality of eggs 

 with which we have begun forms no 

 intergral part of our personal task, 

 what we have to say under this head 

 partakes rather of the nature of inci- 

 dental gleanings and musings than of 

 deliberate investigation. We have at- 

 tempted to enunciate some of the prob- 

 lems without pretending to do more 

 than suggest what may be the nature 

 of some of the solutions. 



Examine on the sea-shore the egg- 

 capsules of a dog-whelk (Purpura la- 

 pillus). If one of the freshly deposit- 

 ed cases be opened in its interior a 

 large number of minute eggs may be 

 counted. Some time later visit the 

 same spot and open others belonging to 

 the same bunch. The probability is 

 that the enumeration of the develop- 

 ing organisms in all the egg-cases of 

 the bunch will not give as large a num- 

 ber as that already recorded in the sin- 

 gle freshly-deposited one. 



This is of course an old story. The 

 cannibalism of the developing young 

 of the dog-whelk and whelk is one of 

 the commonplaces of marine zoology. 



Many years ago the writer endeavor- 

 ed to study it for himself, but as the 

 examination of the cases was begun, 

 when, as it turned out subsequently, 

 the eliminative process was over, it 

 was naturally not observed; although 

 the facts were looked for until the 

 young whelks emerged from their 

 cases. The process on that occasion 

 was not seen, simply because it hap- 

 pens at a very early period. One in- 

 teresting little point, did, however, re- 

 veal itself, that the number of young 



