540 Bashford Dean Memoria] Volume 



As early as 1867, Coste described how a pair of spotted dogfish, Squalus (ScylJium ?) 

 catulus were introduced into the vivarium at Concarneau (a rock-encircled arm of the sea 

 shut off by gratings ). The female extruded 18 eggs during the month of April, and the 

 young were hatched out during the month of December. Thus the period between 

 laying and hatching -^^as about 8 months — not ""about 9" as stated by Coste. 



Bolau f 1881 1 is more exact. On April 12, 1877, the Hamburg Aquarium received 

 from the Brighton Aquarium a number of eggs of the European dogfish, Scyllium canicula, 

 (how long after extrusion is not stated). Four of these hatched as follows — December 3, 

 1877, and January 1, 4, 17, 1878. Their periods were 235. 264, 267, 280 days— from 7 

 months and 21 days to 9 months and 10 days. Seven eggs ot the catshark, Sc\'lliu7n 

 catulus (also from Brighton), hatched from August 19 to October 16 — a time space of 

 129-187 days or 4 months and 9 days to 6 months 7 days. That same season an egg laid 

 in the aquarium hatched in 180 days. During 1878 a number of catshark eggs were de- 

 posited in the same aquarium and 10 of them hatched in periods varying from 157 to 178 

 days or from 5 months and 7 days to 5 months and 28 days. 



These are the known lacts, but more data are needed. In comparison there is reason 

 to beHeve that, while incubation is going on, the temale frilled shark is living in ^x-ater ot 

 probably not over 43°F. (at a depth of 1800 feet.). But what were the ranges of tempera- 

 ture to which the dogfish eggs were exposed at Concarneau and at Hamburg? We have 

 already noted the great size of the egg of Chlamydoselachus. Bolau tells us that the barrow- 

 or stretcher-shaped eggs of Sc>'IIiu7n camcula were 110 mm. long (over the hornsj by 

 41 mm. broad (over the case). The corresponding measurements of the similar eggs of 

 S. catulus are 60-55 mm. long by 24-22 wide. The sizes of the yolk masses in these eggs 

 are not given, but they are undoubtedly far smaller than those ot Chlamydoselachus — 

 probably not more than one-third to one-fourth as large. 



If it takes these relatively small eggs of the European dogfishes from 5.5 to 9.5 

 months to hatch at the spring, summer and autumn temperatures of the English Channel 

 and the North Sea, how much longer must it take for the huge eggs of the frilled shark to 

 hatch at the uniformly low temperatures of 1800 to 3600 feet do\^Ti in the Sagami Sea? 

 At first I u^s incHned to think that the incubation period lasted at least one year. But 

 since Kyle (Biolog}^ of Fishes, p. 66) says that the embryo oi Acanthias takes about a year 

 to develop, it seems probable that it wiU take at least two years tor the embryo of Chlamy 

 doselachus to attain its fuU development. 



It is unfortunate that Dean did not get large frilled-shark embryos later than Klay 1. 

 and larger than the longest of that date (390 mm., yolk 100 x 70 mm.;, with yolks either 

 gone or nearing resorption. Such data would be of great value not only for the question 

 under consideration, but for giving an idea of the amount of distention ot the uterus ""at 

 term", and as indicating the size of the young shark at the time of birth. It is also unfortu- 

 nate that no young free-swimming sharks were taken in the intensive deep-sea hook- 

 trawl fishing carried on in the Sagami Sea by Kuma and the market fishermen. The 

 smallest free-swimming specimen (a female) recorded by Dean measured 1240 mm. (48.8 



