The Emhryology of Chlamydoselachus 549 



light streaks in the figure. Follicular blood vessels are shown as a dark network. This 

 rich vascular network is concerned with the nutrition, development and growth of the 

 huge egg. The circular area in the upper part of the figure is presumably a thin region of 

 the ovarian membranes where the follicle will rupture to allow the egg to escape into the 

 body cavity. It would seem that this egg is practically mature. 



Among Dean's records I find a photograph (Text-figure 12) of an ovarian egg. Study 

 of the detailed markings in drawing and photograph shows both to have been made from 

 the same egg. The drawing was probably made first, the photograph possibly after the 

 egg had been hardened and when a portion of the yolk had been torn away as shown in 

 the photograph. The text'figure is reproduced in the sizie of the original drawing so that 

 an accurate idea may be had of the natural size of this mature ovarian egg. 



In this photograph the limits of the circular area shown in the upper part of Figure 1, 

 plate I, are more sharply defined. Similar areas are visible in five of the large but immature 

 eggs in the ovary shown in situ in Dean's photograph referred to above. On ovarian eggs 

 Nos. 4 and 5, recorded in the Hst from Columbia University and mentioned in a preceding 

 paragraph, are found similar areas. Upon dissecting off the follicular membranes from the 

 circular area in one of these ovarian eggs, there was found a whitish region of correspond' 

 ing shape and size, which presumably represents the germinal area. This area is surround- 

 ed by a shallow depression — a circular groove. The remainder of the egg is a dark yellow 

 and appears to be composed entirely of yolk. I therefore conclude that the circular area, 

 represented in Figure 1, plate I, and in Text-figure 12, overlies the germinal area and is of 

 about the same size. It would be very desirable to study this egg but it cannot be found 

 among the specimens from Columbia University at my command. 



When the ovarian follicles break, the ripe eggs in some way, as yet not clearly 

 understood, find their way into the funnel of an oviduct, and begin their descent into 

 this tubular organ in which fertilization, shell formation and gestation take place. 



THE OVIDUCTS 

 As in other sharks, the oviducts are elongate paired organs joined at their anterior 

 ends where they communicate with the abdominal cavity through wide funnel-shaped 

 openings or sometimes through a single median aperture. Posteriorly each opens separate- 

 ly into the cloaca. When an egg gains entrance into an oviduct through the funnel, it is 

 fertilized by a spermatozoon, passes into and remains in the shell gland while the keratinoid 

 shell is being formed around it and then it descends into the uterine enlargement where 

 segmentation, gastrulation, and the formation and growth of the embryo take place. 

 There will now be considered some interesting features relating to these divisions of 

 the oviduct. 



THE ABDOMINAL OPENINGS. 



In Chlaynydoselachus the abdominal openings of the oviducts are of particular interest 

 because of their variability. These variations will now be pointed out. 



In Carman's specimen (1885), each oviduct (Text-figure 8) has its own opening 

 widely separated from the other. Hawkes (1907, p- 475) does not state how many female 



