4496 Insects. 



remnant of the yolk in the chick. I at first thought it was about to 

 be enclosed in the alimentary canal, but it was not so. As the em- 

 bryo grows it assumes the position of the ovarium, and becomes 

 divided into oval masses and enclosed by the filamentary extremities 

 of the eight oviducts. Individual development is checked and ar- 

 rested at the apterous larval condition. It is plain, therefore, that the 

 essential condition of the development of another embryo in this larva 

 is the retention of part of the progeny of the primary impregnated 

 germ-cell." 



This view of Owen, so ingeniously advanced, and which he has 

 made subservient for the chief support of his new doctriue of Parthe- 

 nogenesis, is indeed plausible, and seems at first satisfactory ; but, as 

 I hope to show, it will not bear analysis. 



In the first place, it is evident that Owen does not recognise any 

 physiological difference between a bud and an ovum : this is clear 

 from what he remarks in the first quotation, but in his work on Par- 

 thenogenesis he has said so in as many words. " The growth by cell- 

 multiplication producing a bud, instead of being altogether distinct 

 from the growth by cell-multiplication in an egg, is essentially the 

 same kind of growth or developmental process." Here is a funda- 

 mental error, which if not removed will obscure all our views of the 

 physiology of reproduction. I have already insisted upon the neces- 

 sity of this broad distinction between these two forms, — a necessity 

 based not only upon differences of anatomical constitution, but also 

 upon physiological signification. An ovum is the exclusive product 

 of an individual of the female sex, and is always formed in a special 

 organ called the ovary. It is the particular potential representative of 

 the female, and has its ulterior development only from its conjunction 

 with a corresponding element of the opposite or male sex ; and 

 Zoology presents no instance where there is development from eggs 

 unless these conditions of the two sexes are fully carried out. A bud, 

 on the other hand, is simply an offshoot from the form on which it 

 rests, a portion of the animal capable of individual development. It 

 sustains, therefore, no relations to sex, and, in truth, is widely sepa- 

 rated in its ulterior signification from that cycle of processes conceived 

 in a true oviparous reproduction. All physiologists who have care- 

 fully studied embryological and developmental processes must feel the 

 correctness and importance of this distinction, which lies in realities 

 and not in words. It is true that a bud and an ovum are composed 

 each of the same elements, — simple nucleated cells ; but in one these 

 cells are simply in a mass, while in the other they have throughout 



