DEVELOPMENT OE THE OVARIES IN THE BLOWFLY. 
439 
paralleled phenomenon. I am by no means sure that it is so. 
The changes in the germarium of the Trematodes described by 
Yan Beneden (5) appear to me to indicate a similar condition. 
The nature of the germ-ova in these has been discussed with 
great heat, some holding that the germ is a naked nucleus, and 
others that it retains a thin, scarcely demonstrable, layer of 
protoplasm around it. 
6. Until the actual passage of such a germ into the yelk has 
been repeatedly observed, I admit that a serious hiatus exists in my 
hypothesis. I am far from sure that the phenomenon has not 
been already observed ; at any rate a passage in Leydig’s mono- 
graph (17) on the ovaries and seminal pouches of insects is 
worthy of note in this relation. Speaking of the chorion of 
Musca clomestica, he says, “ this has at the upper pole of the egg 
a prominent micropyle which appears blocked by a highly refrac- 
tive corpuscle. The corpuscle is not present in all the eggs, and 
may be perhaps an exuding yelk-drop I would ask, may it 
not equally have been an entering germ-yelk ? 
6. Bibliography . 
As the bibliography of the subject is given in extenso by Dr. T\ 
Stuhlmann, 1886 (25), and Dr. A. Brandt, 1878 (6), I shall give 
only a list of the works quoted or directly made use of in this 
paper. 
(1) Balfour, F. M. — Comparative Embryology. 1881. 
(2) Barrois. — “ L’Embryologie des Nemertes.” Ann. Sci. Nat. ser. 6, 
tom. vi. 1877- 
(3) Beneden, E.van . — “ Recherches sur l’Embryogenie des Crustaces.’ 5 
Bull, de l’Acad. R. de Belgique, 2 e ser. tom. xxviii. 1869. 
(4) Beneden, E. v. — Ibid. tom. xxix. 1870. 
(5) Beneden, E. v. — “ Recherches sur la composition et la signification 
de l’CEuf.” Mem. couronnes et Mem. etrang. Acad, de Belgique, 
t. xxxiv. 1870. 
* “ Dieselbe hat am oberen Eipol eine vorstehende Mikropyle und wie 
verstopft durch ein fettglanzendes Zapfchen (Taf. iii. fig. 13d, 14 b). Dieses 
Korperchen ist nicht bei alien Eiern vorhanden und entspricht vielleicht einem 
herausgetretenen Dottertropfchen ” (l. c. p. 35). 
