44 On the Agamic Reproduction of a Species o/" Chironomus. 



This connexion will be rendered clearer by the following 

 table : — 



Ovum of ge- = Germinal ve- + Formative 

 neration 1. side. vitellus. 



Polar cell. = Nucleus of the + Protoplasm, 

 polar cell. 



Embryonal cells. 



A 



Ovarian tube = Nucleus of the + Tunica + Vitelligenous + Epithelial 



I ovarian tube. propria. cells. cells. 



II II. 

 Ovum of ge- = Germinal vesicle. + Vitellus. + Chorion. 



neration 2. 



The ovnm, now fully developed, which originally, as we 

 have seen, had an elongated form, contracts and acquires a 

 spherical form. We see now that the vitelline mass, with 

 the oil-drops enclosed in it, occupies one half of the ovum, 

 the other half being still occupied by the vitelligenous cells ; 

 the nucleus of the germinal vesicle has disappeared ; the epi- 

 thelial cells have become fewer, for where the vitelligenous 

 cells are placed, and where the vitellus is imbedded, they are 

 no longer to be seen, being replaced by the chorion. The 

 ovum does not long retain the spherical form ; before it has 

 become quite filled with the vitellus, its form again undergoes 

 an alteration, becoming oval, and finally egg-shaped. 



Both the summer (pseudova) and winter ova (ova) are 

 developed in the manner above described *. Moreover these 

 two kinds of ova are not distinguished by their structure. 

 Even resting only upon these two facts, we cannot, with 

 Huxley, designate the one form as eggs [ova) and the other 

 as false eggs ( pseudova) . It is true that fecundation is taken 

 as the basis of this distinction, those ova which require fecun- 

 dation for the development of the embryo being called true, 

 and those which furnish the embryo without the aid of the 

 male element false ova ; but even if we are to rely upon the 

 act of fecundation, we must distinguish the product of the 

 development caused by fecundation from the product of the 

 development which has taken place without fecundation, but 

 not the ova, which truly, as Glaus has stated quite correctly f, 

 do not acquire the character of the product of the sexual organs 

 by fecundation. Nay, the designation of the summer ova as 



* Lubbock has found the same thing : according to him the ova and 

 pseudova are developed in accordance with one and the same type ; but 

 " he expresses himself more doubtfully with regard to the origin of the 

 germinal vesicle in the pseudovum " (Keferstein). 



t Glaus, " Beobachtxmgen, &c./' Zeitschr. fiir wiss. Zool. Bd. xiv. p. 51, 



