McCrady.3 180 [April 18, 



undifferentiated and perfectly simple protoplasm capable of develop- 

 ment, of which they themselves are incapable. 



28. So numerous are the examples of parthenogenesis among 

 Insects and Crustacea (Entomostraca, Rotifera), that some explana- 

 tion of it seems necessary, even under a provisional theory. It is 

 probable that this anandrous mode of production has many various, 

 and perhaps totally different conditions at one time from what it has 

 at another. I have not therefore attempted to give more than a sug- 

 gestion here, which, nevertheless, I think contains an element that 

 cannot be reasonably excluded as an impossibility in any case. The 

 suggestion is that 



29. In parthenogenesis the germinative vesicle takes no share in 

 the formation of the new individual, which is strictly a development 

 of the protoplasm of the yolk, which may be regarded as a bud from 

 the maternal ovary. The egg of the queen bee, for example, may be 

 regarded as a bud" from the ovary. If the germinative vesicle receive 

 the influence of the spermatozoa, a new being arises prepotent in de- 

 velopment over the bud. But if not, the hypothesis is that the bud 

 or yolk-protoplasm, may itself develop into a new creature, which in 

 this case will be a drone. In many other insects the same bud will 

 produce a female. 



The provisional theory here explained was framed long before I 

 was acquainted with the observations of Butschli, Fol and Oscar 

 Hertwig upon the early changes of the egg preparatory to, and con- 

 sequent upon, impregnation. It was designed and used as a means 

 of temporarily grouping together the facts hitherto known in accord- 

 ance with the conception of development by specialization, and as a 

 stimulus to further thought and research upon this subject among the 

 students to whom I was called upon to lecture. From them it has 

 found its way to Mr. Minot, who sought and obtained from me some 

 account of it in private conversations referred to by him. 



It has not been possible for me, up to the present time, to make a 

 close examination of the observations referred to (those of Auerbach 

 I have not yet seen), and it is therefore impossible for me to enter as 

 I should much like to do upon a critical review of the present state of 

 our knowledge on this important subject. I have, however, been 

 myself surprised at the harmony between some of the conceptions to 

 which I was led by a general induction from the previously known 

 facts, and the phenomena as actually observed. Thus the germina- 

 tive vesicle, according to Butschli, spreads itself over the surface of 



