272 ME. H. M. BEENABD ON THE 



On the Spinning-Grlands in Thrynus; witli an Account of the 

 so-called " Penis " and of the Morphology of the Operculum. 

 By H. M. Beenaed, M.A. Cantab., P.L.S., F.Z.S. 



[Eead 20tli December, 1894.] 

 (Plate VIII.) 



A FEW months back my friend Mr. E. I. Pocock, of the British 

 Museum, called my attention to the fact that, in tearing the 

 cocoon oi Phrynus, short threads were drawn out, which seemed 

 to indicate the presence of spinning-glands ; and he suggested 

 that I should investigate the point. On clearing and mounting, 

 the cocoon appeared to be a tough yellowish transparent mem- 

 brane strengthened by threads which wound about it without 

 any regularity, but which evidently formed the attachment of the 

 cocoon to the under surface of the operculum. These threads 

 varied greatly in thickness, being here uniformly thick, there 

 uniformly thin, again elsewhere changing gradually from thick 

 to thin. 



Two young specimens at my disposal (unfortunately not 

 well preserved) were cut into serial sections without, however, 

 revealing any traces of spinning-glands. It seemed, therefore, 

 highly probable that (as in the Chernetidae) the spinning-glands 

 in Phrynus are subject to periodic variations, i. e. develop only 

 when required for the formation of the cocoon. 



Light has, however, recently fallen upon the subject from 

 an unexpected source. My attention was called (again by 

 Mr. Pocock) to the so-called " penis " of Phrynus, which occurs 

 presumably in the males. I had never seen this structure although 

 I had examined a good many specimens of Plirynus. I had found 

 it figured by Blanchard, who also calls it a penis. In order to 

 facihtate the investigation, Mr. Pocock kindly allowed me to 

 examine a specimen of Tarantula tessellata, Poc.*, belonging to 

 the Natural History Museum, and also an excised " penis " 

 which he had in his possession. As I was unable to dissect or 

 section the specimens, the description can only be complete 

 as far as it goes. 



* Described and figured in ".Arthropod Fauna of the West Indies," Jouru. 

 Linn. Soc, Zool. xxiv. p. 531. 



