34 O. NORDGAARD [1915 



As proof that the dorsal fin persists in its original position, I 

 give the following figures : 



.ength of embryo oi' 



Distance from 2. dorsal fin 



R. radiata 



to point of tail 



23 mm. 



8 mm. 



32 



10 



40 



15 — 



60 



16 



94 



17 



102 



17 



103 



17 



The embryo of R. radiata examined by Jensen measured 

 130 mm. total length; the distance from 2. dorsal fin to point 

 of tail was here no less than 27 mm. (vide footnote 2, 1. c. p. 17). 



The table above shows, that the distance from the original 

 indication of dorsal tins to point of tail increases during devel- 

 opment, and reaches its maximum at the close of the capsule 

 period. As this tail point has never, so far as I am aware, been 

 observed in free young specimens of R. radiata, the only expla 

 nation must be that the part behind the dorsal fins falls off 

 either just before or immediately after the young emerge from 

 the capsule, and commence their free existance. In pl. II, figs. 

 6 and 7, this prolongation of the tail is very distinctly visible. 



It would be natura! now to ask, whether this point of tail 

 is of any imporlance to the embryo during its development. 

 The answer must be, that this is most unlikely. The prolonga 

 tion of the tail is not a necessary apparatus, but must be here 

 ditarily derived from earlier long-tailed forms according to the 

 biogenetic law. On the other hand, this small stump of tail 

 serves to show, that the long-tailed rays are older than the 

 short-tailed in the phylogenetic development. 



Raja nidrosiensis Coll. 



The egg capsules of this species (Norw. : svartbukskate) are 

 mentioned both by Collett and Swenander. The former 1 

 gives the length of the capsule from middle of anterior trans 

 verse edge to middle of posterior do. as 220 mm., breadth 95 

 mm., and comparatively short terminal tubes (abt. 30 mm.). 

 Swenander 2 obtained in January 1905 in Trondhjem Fjord, a 

 female with one fully developed egg in each of the oviducts. 

 The dimensions of the egg capsules were 200 X 120 mm. 



In a $ of R. nidrosiensis, tåken in the Munkholm deep 20 /s 



1 Meddelelser om Norges Fiske 1884—1901, III, p. 128, Kristiania, 1905. 

 - Bidrag till Kånnedomen om Trondhjemsfjordens Fiskar. D. kgl. 

 n. vid. selsk. skr. 1905, nr. 9, p. 77. 



