589 



CHAPTER XII. 



GENERATIVE PRODUCTS AND DEVELOPEMENT OF 

 HJSMATOCRYA. 



The functions of the above-described Generative Organs are 

 ' semination,' ' ovulation/ ' fecundation,' and ' exclusion,' to which 

 is added, in some Hajniatocrya, that of e fcetation.' Semination, 

 or the production of sperm-cells, is peculiar to the testis : ovula- 

 tion, or the production of germ-cells and vitellus, is peculiar to 

 the ovary : fecundation is the combined act of the male and 

 female. A part of the oviduct is usually modified to add 

 accessory parts to the ovum, or in subserviency to fcetation in the 

 viviparous H&matocrya : but, in a few instances, the protective 

 and portative functions are relegated to tegumentary wombs or 

 marsupia, whichmay be developed in either sex. Exclusion of the 

 male generative product is called ' emission,' that of the female 

 generative product c oviposition : ' but if the ovum be arrested for 

 the process of fcetation, the exclusion of the foetus is then termed 

 ' birth.' Sometimes the male assists in the process of exclusion. 



§ 111. Semination of Hamatocrya. — The product of the testis 

 in Fishes consists of ' sperm-cells,' ' spermatoa,' and 'spermatozoa,' 

 with very scanty fluid medium of suspension : the function is 

 seasonal, and attended by 

 rapid increase of the glands. 3 " 



This is greatest in Osseous 

 Fishes, in the testes of which, 

 at the beginning of their 

 enlargement, the sperm-cells 

 (cysts or 'mother-cells') are 

 seen, fig. 399, a, containing 

 one or more spermatoa (' cells 



of developement '), ib. b. These usually escape from the sperm-cell 

 as such, and then undergo some change of shape, through the deve- 

 lopement of the spermatozoa within them. The rupture of the 

 spermatoon gives issue to the extremely fine capillary appendage, 

 or ' tail,' the movements of which extricate the nuclear mass forming 

 the so-called ' body ' of the spermatozoon. In most Osseous 



Sperm-cells with spermatoa, Bream, cccvi. 



