SEXUAL CHARACTERS — ELASMOBRANCH FISHES 241 



manner as when the other branches are left intact, so that antero- 

 flexion of the clasper is brought about. In fine, the antero- 

 flexion helps to originate the erection and is normally part of it, 

 though, on nerve severance, erection alone can still be induced 

 by stimulation. 



Secretion of the clasper gland takes the form of the protrusion 

 of long, glairy, transparent strings of substance from the papillae, 

 suggestive of the squeezing out of an artist's oil colors from their 



Fig. 18 Raia clavata. A diagrammatic representation of the secretion of a 

 smgle string of albumin from a papilla of the clasper gland. 



containing tu]:>es. For the sake of simplicity, only one such string 

 is shown diagrannnatically in figure 18. This substance exhibits 

 all the chemical and physical properties of albumin; hence the 

 clasper gland must in the future be considered an albuminous 

 gland. Long strings of albumin in an undisintegrated state were 

 found lying in the siphon sacs of fresh skates dissected for 

 practice which had died a 'natural' death, without resort to 

 electrical or other stimulation. The secretion of man}^ papillae 

 at once is very striking to observe. Since all do not secrete 



