402 University of California Publications in Zoology. [ VOL - 6 



consequently were full of fully formed ova, having the nature of distinct 

 cells with clearly defined nuclei. In the second the uterus was full of 

 much more highly developed embryos, and no ova, apparently, were pass- 

 ing into it. In this case the ovaries were evidently in the act of develop- 

 ing a fresh supply of ova. Each consisted of a mass of protoplasm con- 

 taining nuclei, evidently dividing rapidly, whilst the outlines of the cells 

 could only here and there be seen with anything approaching to clearness. 

 Each little ovary has thus, when the ova are not fully formed, the struc- 

 ture of a polynuclear mass of protoplasm, which only subsequently 

 becomes divided up into a number of distinct cells. ' '1 



In all the preparations studied by the writer, the ovaries con- 

 tained at the same time both fully formed and developing ova; 

 the uterus contained young embryos in its most posterior coils, 

 and older ones towards its anterior opening. It seems that in 

 G. fimbriata the process of egg formation goes on uninterruptedly 

 the year round, rather than in a rhythmical fashion, as indicated 

 for G. rugosa by Spencer 's observations. This may be correlated 

 with the fact that apparently the period of intra-uterine life is 

 longer in G. rugosa than in any other species, this being the only 

 form in which the uterus contains hooked embryos. 



Each follicle of the ovary is surrounded by a fibrous layer, 

 called by Lonnberg the "tunica propria," continuous with the 

 walls of the oviducts into which the ova are discharged. Plate 

 41, figure 52 represents a typical follicle with ova in early stages 

 of development. There is a syncytium containing small, round 

 nuclei with recticular chromatin and either a very small nu- 

 cleolus or none whatever. The other half of the same follicle is 

 cut up into cells with definite walls, denser cytoplasm, clear 

 nuclei nearly double the size of those in the syncytium, with 

 dense marginal chromatin reticulum and very large excentric 

 nucleolus. Plate 41, figure 53 represents stages intermediate 

 between these two, showing the growth of the nuclei and par- 

 ticularly the appearance of a large extra-nuclear body, staining 



i Dr. M. Hungerbiihler's "Studien an Gyrocotyle und Cestoden " 

 (1910) was received too late for its results to be incorporated in the body 

 of this paper. He makes the suggestion, based on the facts above quoted 

 mentioned, that Spencer was dealing with two different species of Gyro- 

 cotyle, that is, with G. urna and G. rugosa. While this explains numerous 

 discrepancies in Spencer 's account, and while my own results show the 

 presence of two species of Gyrocotyle in one species of Chimaera, yet the 

 forms described by Spencer differ widely in several essentials from G. 

 urna, and Hungerbiihler 's grounds for concluding that one of Spencer's 

 forms was G. urna do not seem adequately to account for these differences. 



