The Embryology of Chlamydoselachus 565 



notes read "I. ovar. very small, r. nearly twice as large". A solitary C. platyodon had 

 the left ovary small and the right large with eggs in the anterior part. Both these sharks 

 had both oviducts well developed and functional. 



Of the genus Hypoprion, I dissected two species — H. hrevirostris and H. signatus. 

 In each, the oviducts were bilateral and functional, but the left ovary was small and with' 

 out eggs; the right ovary was large and functional with eggs in the anterior end. The 

 same condition of oviducts and ovaries was also found in ScoUodon terranovae. 



From these data on some of the tropical sharks of the eastern Gulf of Mexico, it is 

 plain that they are on the way toward unilateral functioning of the reproductive organs. 

 They have not gone so far in this matter as has Chlamydoselachus, since both oviducts 

 are functional while only one ovary (the right) produces eggs. No reason for this can 

 now be given, since they are sizable sharks with large abdominal cavities. This is especial' 

 ly true of the flat-bodied Ginglymostoma, in whose roomy abdomen are contained large 

 uteri which when gravid much resemble in si2;e and shape a pair of old'fashioned saddle' 

 bags. This size and form make it possible for each to contain, or are conditioned upon its 

 containing, 20-21 eggs c. 140 mm. long x 185 in circumference. From these sharks with 

 partial unilaterality of genital organs, we now pass to the rays in some of which complete 

 unilaterality has been attained. 



OVARIES AND OVIDUCTS OF VARIOUS RAYS 

 The rays are elasmobranchs flattened in the dorsoventral or vertical plane to fit them 

 for bottom'living. They comprise the most specialized group of the Elasmobranchii. 

 They are referred to here because there are found in these viviparous fishes the same vari' 

 ations in the reproductive organs that are found in Chlamydoselachus, the reputedly 

 lowest form of the strap-gilled fishes. There is an extensive literature on this subject 

 but I shall confine myself to my own researches. 



Pteroplatea maclura. — The butterfly ray is abundant at Beaufort, N. C In 1912 

 (Gudger, 1913) I dissected four female specimens. The reproductive organs of both sides 

 were functional, but in every fish the left ovary was better developed than the right 

 (in fish No. II, 25 per cent larger). Furthermore, in each case the left uterus was better 

 developed and contained more eggs. Fish No. I had three eggs in the left uterus and an 

 empty shell (wind egg) in the right; No. II had one egg (but with two yolks) in 1. and 

 an imperfect egg in r.; No. Ill had two eggs in 1. (one with a malformed shell) and one in 

 r.; No. IV had both uteri gravid but left twice as large as right. Unfortunately these 

 two uteri were not dissected. 



It is significant that in this ray the reproductive organs of the left side are better 

 developed and more functional than those of the right. This is just the reverse of con- 

 ditions in Chlamydoselachus. Another notable point is that imperfect eggs are found in 

 both uteri of the ray. Parenthetically it may be noted that this same condition seems to 

 prevail in the nurse shark. From all these data, I draw the conclusion that Pteroplatea 

 maclura is in an intermediate stage between those rays having perfect bilaterality of the 



