SEXUAL CHARACTERS — ELASMOBRANCH FISHES 365 



There are certainly two, probably three and possibly four 

 breeding seasons in a year. Speaking from my own experience 

 of Scyllium canicula from Plymouth and Bournemouth, the 

 seasons are: 1) April to May; 2) July to August. Whether the 

 season May to June is an extension of number (1) I am in doubt, 

 and of a season in January should like further corroboration. 

 The indications of the breeding season are: 1) Spermatozoa 

 oozing from dead males on pressure of the finger on the urino- 

 genital sinus; 2) spermatozoa oozing from dying or maimed 

 Dover topes; 3) the presence of ova in the oviducal gland about 

 to be coated with a ^shel^ case. Breeding seasons for the same 

 species may vary with, 1) weather; 2) locality, both factors 

 being modified by temperature. 



I was interested to notice that on handling a vigorous, strongly 

 secured wounded male tope I could feel pulsations which pre- 

 sumably were those of the siphon. Spermatozoa did not in this 

 case spurt from the clasper tip, but from the cloaca. On bend- 

 ing the claspers forward some ejection from the tip was obtained, 

 but slight because the clasper is not a scroll-tube as in Scyllium, 

 whereas in copula the oviducal wall would help to form a closed 

 passage. Moreover, the tope must have been pumping sper- 

 matozoa with air, since its siphons had long been emptied of 

 water in its struggles. 



MUSTELUS VULGARIS 



The smooth-hound 



In Mustelus the siphons attain even larger dimensions than in 

 Galeus, extending almost as far forward as the pectoral fins. 

 In the specimen upon which the following observations were 

 made, taken at Plymouth in July, 1918, and which measured 

 54 cm. from the tip of the snout to the posterior ends of the 

 claspers, the siphons were 23 cm. in length, so that they cannot 

 be included in their entirety in the figure (fig. 5). 



As in Galeus, the claspers project considerably beyond the 

 pelvic fins posteriorly. The clasper tube is closed for the greater 

 part of its length, the edges overlapping in a scroll-like manner 



