OVARY AND OVA IN LUCIFUGA AND STYGICOLA. 227 



The size of the ovary varies with the age and size of the females as well as the 

 state of development of the embryo or ova within it. One specimen, a Lucifuga 

 65 mm. long, had an ovary only 16 mm. long and 8 by 9 mm. in largest diameters, 

 altho it contained 4 nearly ripe young, each 18 to 20 mm. in length. One non- 

 pregnant Lucifuga,&T, mm. long, had an ovary but 12 mm. in length. These meas- 

 urements were made on preserved specimens. 



The point of division into the two horns is usually a little less than halfway from 

 the anterior tip of the ovary to its posterior end. The two horns themselves are 

 rarely equal in size, though there is no evidence of any tendency toward an unpaired 

 condition through the "phylogenetic resorption" of one side such as Ryder found in 

 Gambusia patruelis. 



The space between the ovisac and the inclosed ovary varies in size and is con- 

 tinuous with the lumen of the oviduct. The growth of the young results in a grad- 

 ual stretching of the ovisac, and to a certain extent of the oviduct also, so that near 

 the close of gestation these structures are so extremely thin that their cellular nature 

 can not be satisfactorily made out (plate 29, figs. A,B,C). Apparently within a short 

 time after the birth of the young, the ovisac and oviduct contract and reassume the 

 form and appearance found in the ovaries of mature non-pregnant females. The wall 

 of the ovisac is then quite thick (ov.s., plate 29, fig. D) and the lumen very small. 



The stroma of the non-pregnant ovaries is a bilateral mass which occupies most 

 of the space within the ovisac. Its general shape resembles that of the ovisac, 

 being fusiform in its main part, with its greatest diameter just posterior to the 

 division into the two horns. The horns of the stroma are attached to the horns of 

 the ovisac along their median surfaces (plate 29, fig. A), the whole stroma 

 forming a V. In the stem of the V the stroma forms a median dorso-ventral 

 partition within the ovisac, which is to be looked upon as representing the area of 

 fusion of the originally distinct right and left ovisacs (fig. B). Near its posterior 

 end this partition is cut across laterally by a fissure and the two prongs thus formed, 

 one dorsal, the other ventral, gradually disappear toward the oviduct (figs, c and 

 D). Sometimes the dorsal one disappears first, sometimes both are equally extensive. 



The stroma has many somewhat pointed and comparatively large lobes, which 

 are usually connected with the main mass by a slender "neck" of tissue. Dr. 

 Eigenmann observed that these lobes are sometimes held in the mouth of the young 

 fish during a part at least of its later development. Whether the young derives 

 any nourishment from the lobes can not be stated with certainty. The whole stroma 

 in the non-pregnant ovaries is distended by a large amount of lymph and adipose 

 tissue contained in the sinuses described below, especially when approaching the 

 reproductive period as shown by the maturity of the ova. 



The largest ova can be seen through the ovisac by the unaided eye as opaque 

 white dots in the preserved specimens (plate 27). The follicles surrounding these 

 ova usually lie some distance beneath the surface of the stroma and a tubular inden- 

 tation of the epithelial covering of the latter extends down to the follicle (plate 29, 

 fig. E). The blind end of this pit is so closely applied to the follicular membrane 

 that it usually requires a very close inspection to discover its independence. It is 

 then found that the follicular membrane at this place is only a single cell layer in 

 thickness. Stuhlmann describes a similar indentation of the epithelium over the 

 ova in the ovary of the viviparous blenny, Zoarces viviparus Cuvier. 



