The Emhryohgy of Chlamydoselachus 615 



line. The paired fins have well'deve loped bases. The dorsal and anal fins look much like 

 those in the adult fish and even more is the caudal like the tail fin of an adult Chlamydo- 

 selachus. The tropeic folds, noticeable in the 103'mm. fish, are here plainly visible. 



Head in Ventral Aspect. — The list calls only for "Embr. 185 mm. lateral aspect". 

 It does not call for ventral view of the head, but such a drawing I find. This is reproduced 

 as Figure 47, plate IV. The next youngest head in like aspect with which it can be 

 compared is that of the 103'mm. embryo (Figure 43, plate IV). Here one sees that the 

 profuse external gill'filaments of the 103'mm. head are reduced to mere remnants in 

 the gill'slits of the 185'mm. fish. Furthermore, the mouth of the older fish looks more 

 finished, more nearly adult. The first gill'flaps are continuous across the isthmus. These 

 flaps show some evidence of being ''frilled". In the 103'mm. embryo, the yolk stalk has 

 been cut off close to the body. In the 185'mm. fish the basal part is shown attached to 

 the body. This is very large and I judge that here it is really part of the sac that is seen, 

 that we have here the attachment of body to yolk directly comparable to that seen in the 

 390'mm. shark portrayed in color (Figure 49, plate V). 



A Young Frilled Shark 240 mm. Long 



The next embryo on the "List" is one of this size to be drawn in full length, lateral 

 aspect, without yolk. This little fish was drawn slightly smaller (3 mm.) than natu- 

 ral size. As Figure 48, plate IV. shows, it is even more like the adult than is the 185' 

 mm. specimen (Figure 46, plate IV). The long mouth has nearly attained the terminal 

 position, nostril and eye call for no remarks, the gill'flaps are frilled and show short 

 filaments in the openings. There is a small spiracular opening precisely in its adult location. 

 All the fins are better developed and even more closely resemble the adult organs than 

 those of the preceding stage. The lateral line runs the full length of the body and shows 

 only very slight variations under the dorsal fin in contrast with both the 185- and the 

 124'mm. young. The little fish is still attached to its yolk sac by a cord 7 mm. in diameter. 

 The caudal, like that of the I85'mm. fish, is slightly bent upward. 



A J90'MM. Chlamydoselachus in Natural Colors 



Next and last. Dean's "List" calls for four embryos to be drawn. These were "taken 

 about May 1, 1905", and were "Bt. in Tokyo, June 20". They measured in millimeters 

 317, 331 (yolk sac. 111 x 100), 352 and 390 (yolk sac, 100 x 90), and probably all came from 

 one mother. However, since they were presumably twins and since the youngest differed 

 from the largest embryo by only 38, and the others by 59 and 73 mm. respectively, it was 

 clearly unnecessary to go to the expense of having all four drawn. So Dean seems to 

 have compromised by having the largest specimen drawn in color. This exquisite drawing 

 is accurately reproduced in the original colors as Figure 49, plate V. 



It may be of interest to attempt to reconstruct the history of the specimen and of the 

 drawing. Since the four embryos were "taken about May 1, 1905" and "Bt. in Tokyo, 

 June 20", they must have been in preservative about seven weeks before they came into 

 Dean's possession. Now Dean states (1901) that he had the active cooperation and 



