558 MR. E. W. L. HOLT OX TUB [JuilC 21 , 



eye of the male is known to enlarge as a secondary sexual 

 character associated with the development of other structural 

 changes; while according to Grassi ' the Common Eel (Aw/villa 

 vulgaris) acquires large eyes in deep water and in the Eoman 

 cloacae. The secondary enlargement of the eye in ScojieJus is 

 thus not without parallels. Scopelus is, I suppose, a form driven 

 from littoral regions to a pelagic and bathybial mode of life, 

 iuvolving an enlargement of the visual apparatus. 



Among the pelagic fishes enumerated by Giinther in his 

 ' Challenger ' monograph (vol. xxxi.) are mentioned a number of 

 small Scoj)e7i taken by the ' Triton ' in the Faeroe Channel {luc. cit. 

 p. 31). While recognizing the close resemblance which these 

 forms bear to S. gUtcialis, the author considers that certain 

 characters deserve specific distinction, and has accordingly de- 

 scribed them under the name of S. scoticus. 



The largest specimen measures 14-5 mm., that is, exactly the 

 same as the S. glacialis shown in figure 1. In the dimensions of 

 the eye (naturally considered by Giinther, in the absence of any 

 information of the deAelopmental changes of this organ, of 

 importance) the two forms are in practical agreement. The 

 contour of the snout appears to agree with the corresponding 

 stages in Dr. Fowler's collection. The posterior margin of the 

 preoperculum is described as vertical in S. scoticus, it is rather 

 oblique in S. glacialis. In the characters of the maxilla the two 

 forms agree. The photophore formula is described as identical 

 with that of S. glacialis. In *S'. scoticus the origin of the dorsal is 

 nearer to the root of the caudal than to the tip of the snout, and 

 is behind that of the pelvics. In S. glacialis of 14-5 mm. the dorsal 

 arises midway between the snout and the caudal ; in a specimen of 

 11 mm. it is a little nearer to the latter ; and comparison of the 

 several young stages suggests that in relation to the two points 

 named there' is during development a slight variety iu the position 

 and perhaps a developmental migration of the fin. It is behind 

 the base of the pelvics even in adults. Younger stages do not 

 dilfer in any important detail described from those in Dr. Fowler's 

 collection, but specimens of 9 mm. are stated to have the fin-rays 

 perfectly differentiated. In this case the length given appears 

 from the context to include the caudal fin. One specimen of b mm. 

 (without caudal) has the rays of the dorsal still undifferentiated. 

 Individual variation in the degree of development at a given size 

 is, however, a common feature in Teleostean ontogeny. The 

 radial formula of S. scoticus is stated as D. 10/11, A. 16. That of 

 >S'. glacialis is, according to Goode and Bean, D. 12-14, A. lG-18. 

 In Dr. Fowler's specimens the formula, as we have seen, is D. 12 

 or 13 to 14 (?), A. 18 and 18 ca., with the exception of one which 

 has only D. 11 or 12, A. 15 or 16. This last specimen is one of 

 the most advanced, in good preservation, and of nearly the same 

 size as another, from which it differs iu no detail except the 

 number of fin-rays. I believe that all Dr. Fowler's Scopeli can 

 ' Q. J. M. S. xxxix. 1896, p. 385. 



