DR. MARTIN BARRY'S RESEARCHES IN EMBRYOLOGY. 341 



brana oviili externa" of Bernhardt, and its transparent substance is the 

 "spatium pellucidum" oF this author, g^. Ruptured tunica granulosa^ 

 the "zona granulosa" of Bernhardt (Symbolse, &c., fig. xxiii. pp.45. 46.). 



Fig. 73. Ox (Bos Taurus, Linn.), g. Some of the peculiar granules of the ovisac 

 with their nucleus. In one instance a single granule presents two nu- 

 clei (8. 10.). This granule measured Tlirth Paris line in length. 800 diatn. 



Fig. 74. Hog (Sus Scrofa, Linn.). A patch of parasitic ovisacs (h) (57.) in {h i) 

 the parietes of a Graafian vesicle. There is seen in several a tapering at 

 one end (3.). They are all more spherical than when first formed (3.). 

 f. The ovum. 60 diam. 



Fig. 75. Dog {Cams famiUans, Linn.). Part of a Graafian vesicle {h i), with pa- 

 rasitic ovisacs (57.) (h) in its parietes. Compare with fig. 76. from the 

 Pigeon. 100 diam. 



Fig. 76. Pigeon {Columba livia, Linn.). Ovisac with its vascular covering; the 

 union of these two presenting {h i) a structure analogous to the Graafian 

 vesicle of Mammals (47.). In the parietes of this structure, and probably 

 included (57.) on the acquisition by the ovisac of its covering, are several 

 parasitic ovisacs {h). The vesicle has been crushed, but the minute pa- 

 rasitic ovisacs remain unmoved. The yelk has escaped, g. Peculiar 

 granules passing slowly out of the vesicle. Compare these with the cor- 

 responding granules in Mammalia (8 — 10.); and compare the parasitic 

 ovisacs in tliis figure with those in fig. 75. from the Dog. 60 diam. 



Fig. 77' Ox, Heifer {Bos Taurus, Linn.). Ovary, with the outer third of a Graafian 

 vesicle reflected. In the parietes of the Graafian vesicle there is seen 

 transversely divided {h) a parasitic ovisac (58.), or incipient Graafian 

 vesicle. Actual size. 



Fig. 78. Ditto. Enlarged view of the two halves of the divided parasitic ovisac, 

 or incipient Graafian vesicle, seen in fig. 77- /• Ovum ; ^» membrana 

 granulosa ; h. proper membrane of the parasitic ovisac. 



Fig. 79. Ditto. Transverse section of the proper membrane (A) of the parasitic 

 ovisac, or incipient Graafian vesicle, shown in figs. 77- and 78, here re- 

 moved from its proper cavity (6.). The membrana granulosa {g-^) has 

 fallen down. 25 diam. 



Fig. 80. (from Baer). " Ovule avec le disque prolig^re {g^) d'une vache, grossie dix 

 fois." Contrast with fig. 55. Plate VI. 



