of tJic Fishery Board for Scotland. 251 



Xote on the Eejjroduction of the LijtJie. 



In May a male measuring 50"5 cm., and a female measuring 43"7 

 cm,, were immature. A female measuring 87-8 cm. was in June spent. 

 In September a female 72 cm. in length had a developing ovary, and in 

 December two males measuring 71 and 73 cm. were almost ripe. 



According to Mr. Duthio, a few ripe lythe are captured during March 

 in the cod nets at Girvan. 



For other data regarding the spawning of the lythe, see M'Intosh and 

 Masterman, "British Marine Food-Fishes," London, 1897. 



OSTEOLOGICAL DIFFERENCES. 



In addition to the description and measurement of the external 

 characters, this research has included a comparison between the three 

 species in respect to the form of the bones of the head. 



The osteology of Teleosteans has been treated by a large number of 

 'authors, the names of whom it is not necessary here to mention. It is 

 not the purpose of this paper to enter upon the general morphology of 

 the skull, but simply to institute a comparison between the bones of the 

 head of the three Gadids, Cod, Saithe, and Lythe. It is, moreover, not 

 intended to cover the field of development. All the desci-iptions are, 

 unless expressly stated otherwise, made upon the skeletons of large 

 specimens, of which the following is a list : — 



r Males, measuring 82*7, 85 "4, 94, 95.5, 102 cm. 

 Cod <^ Females, measuring 92-7, 103'5 cm 



[ Disarticulated Bones of Skull — male, 95-5 cm.; female, 89 o c??i. 

 j Males, measuring 88-5, 88-9, 90, 98-2, 98-7 cm. 

 Saithe "I Females, measuring 87"5, 90, 96'2 c??i. 



I Disarticulated Bones of Skull — male, 91-1 cm.; female, 90 cm. 

 Males, measuring 70"6, 71*4, 75, 86 cm. 

 Lythe ^ Females, measuring 76-4, 78'4, 78-4, 78-5, 82-9, 878 cm. 



Disarticulated Bones of Skull — male, 69'6 cm.; female, 85'3 cm. 



Since no very evident indication of sexual differences in the skulls of 

 any of the species was made out, the contrasting points which are de- 

 tailed are to be regarded as bearing value quite independent of sex. A 

 considerable amount of variation exists in the skulls of any one species, 

 and difierences due to individual variation were found between fishes of 

 one sex, of as great amount as there were between those of different 

 sexes. 



In instituting the comparison it will be necessary to traverse ground 

 which has been already well opened up — viz., in connection with the 

 osteology of the cod. This is a type which has been much studied ; it 

 has been treated in detail by Owen.* So far as I am aware, no detailed 

 description has been given of the skeletons of the saithe and lythe. The 

 osteology of the haddock {Gadus xglefnus) has been exhaustively treated 

 by St. John Brooks.t 



As might be inferred, the bones of so closely allied species as the three 

 Gadids here treated are on the whole very similar, and the differences 

 are in many cases those of detail. In Plates IV. -XL drawings or 

 photographs of all the bones described are given. 



*Huntcriaii Lectures II. Lectures on the Comparative Anatomy and Physiology of 

 the Vertebrate Animals. Pt. I. Fishes. London, 1S46. 



fThe Osteology and Arthrology of the Haddock {Gadus a:glrfiiius). The Scieniijic 

 Proceedings of the Roi/al Dublin Sociely. [Read, 1883.1 



