Oil Parasitic Castration in Lumbrlcus herculeus. 335 



Family 2. Exocoetidae. 



Prpemaxillai'ies with straight transverse anterior margi a ; 

 maxillaries free from or merely adherent to praemaxillaries ; 

 teeth in jaws minute, villiform ; third upper pharyngeals 

 simply coalesceut, the plate readily separating iato its two 

 components. Vertebrae 44- to 52 ; most of the parapophyses 

 directed somewhat downwards and forwards. Pectoral fins 

 large. 



Genera : Exoccetus, Halocypselus, Parexocoetus, Fodiator. 



EXPLAN.1TI0X OF PLATE IX. 



Dentigerous pharyngeal bones of: A. JExoccetus lineatus; B. Ilemi- 

 rhamphus intermedins; C. Xenentodon caneila; D. Tylosurus 

 acus ; E. Belone belone ; F. Scombresox saurus. The second, 

 third, and fourth upper pharyngeals are numbered. 



XXXVII. — Note on Parasitic Castration in the Earthworm 

 Lurabricus herculeus. By Igerxa B. J. SoLLAS, B.Sc, 

 Newnham College, Cambridge. 



All observations on parasitic castration have acquired fresii 

 interest since the publication of Mr. Geoffrey Smith's work oa 

 the experimental analysis of sex (3) , Also, so far as I know, 

 no case of parasitic castration of a hermaphrodite animal is at 

 present on record. 



The castration described in this note attracted my attention 

 in February 1910, when I found that of ten full-sized earth- 

 worms provided for demonstration purposes five possessed 

 either no clitellum or an imperfectly developed clitellum, and 

 in the abnormal individuals the seminal vesicles were either 

 small and contained no sperm at any stage of development, 

 or they were more or less normal as to size, but contained 

 chiefly immature stages of sperm-cells. The spermathecae 

 were empty ; the ovaries were normal. In those worms in 

 which the degeneration of the seminal vesicles was most com- 

 plete not only was there no trace of clitellum, but the lips of 

 the male duct were not tumid and the genital chgetse were not 

 more prominent than the rest. Further batches of worms 

 were obtained from the same locality, and rather less than 

 half their number proved to lack the clitellum. A number 

 of specimens without clitellum have also been found in various 

 other localities. 



