OVULATION IN MAMMALTA. 709 



CHAPTER XXXVIII. 



GENERATIVE PRODUCTS AND DEVELOPMENT OF MAMMALIA. 



As the leading forms of the Mammalian spermatozoa have been 

 already given, and as their development does not differ in any- 

 essential degree from the process described in Vol. I. pp. 589-592, 

 I proceed to notice the correlative act which is truly characteristic 

 of the present class. 



§ 395. Ovulation in Mammalia. — The ovum in Mammals, 

 characterised by its extreme minuteness, was recognised soon 

 after the microscope came into use.. De Graaf l (1672) discovered 

 it in the oviduct of the Rabbit. Haller, 2 unsuccessful in this 

 quest, lent his authority to discredit the statements of the Dutch 

 anatomist; but Cruikshank 3 (1797) confirmed and established 

 their accuracy. Nevertheless, up to 1824, the Mammalian ovum 

 was known only as it appeared in the oviduct. 



Prevost and Dumas, indeed, twice detected a less pellucid 

 spherical corpuscle, a millimeter in diameter, in the ovarian or 

 Graafian follicle, and deemed it very probable that thence was 

 derived the oviducal ovule. 4 Von Baer (1827) raised the proba- 

 bility to scientific certainty by a series of observations of the 

 ovarian ovum, made in the Bitch, Cow, Sow, Ewe, Rabbit, and 

 also in the Human female. He deemed, however, this ovarian 

 ovule to answer, not to the entire ovum of lower Vertebrates, but 

 to the e germinal vesicle ' of such ; the fluid of the Graafian 

 vesicle he homologised with the f yolk,' and its lining membrane 

 with the ' membrana vitelli,' so that the ( Graafian vesicle ' was 

 still to Von Baer, as to Prevost and Dumas, the f ovum of the 

 ovary.' 5 Soon followed, however, an almost simultaneous series 



1 CCLVl". 2 CC'LVIl''. 8 CCLVIIl". * CCLIX". 



5 ' Vesicula ergo Graafiana cum ad ovarium generatimque ad corpus maternum 

 respiciamus, ovum sane est tnammalium. Sed evolutionem quod attinet, vehementer 

 discrepat a reliquorum ovo animalium, quorum ovi nucleus integer ex ovario deve- 

 hitur, fetui nascituro non sedem tantum prsebiturus sed in ipsum potius fetum trans- 

 formandus. In mammalibus vero vesicula innata vitellum magis excultum continet 

 et ratione ad fetum geniturum habita verum sese probat ovum. Ovo fetale dici possit 

 in ovo materno. Mammalia ergo habent ovum in ovo aut, si bac dicendi formula uti 

 licet, ovum in secunda potential— P. 32: 'Quapropter in vesicula Graafiana describenda 



