20 



Jfirst annual Report 



available material allow comprehensive work on any one group. 

 Consequently the accompanying notes and figures relate to many 

 widely separated species, so that little comparison can be made ex- 

 cept iu a general way. Since, however, none, or very few of these 

 common forms have ever been studied or described from the point of 

 view of internal structure it is thought well to include herewith all 

 the information gathered. It is interesting to note, even in what is 

 included, the many modifications and variations that arise. Some of 

 these are easily explained by the habits or food of the species, as for 



Figures 1 and 2. Rhinobatus productus 



Fig. 1, Ventral view of entire viscera, in natural position. Fig. 2, Same with 

 organs separated to show form. The liver is thrown back, the alimentary canal 

 stretched out, and the uro-genital organs pulled to one side. J, Liver. O, Ovary. 

 Q, Kidney. D, Oviduct. R, Rectal gland. X, Spleen. Y, Pancreas. Numbers 

 refer to corresponding regions of the alimentary canal. 



Figures 3 and 4. Aetobatus californicus 



Fig. 3, Ventral view of viscera entire. Fig. 4, Same with organs separated. 

 A, Vent. D, Spleen. E, Pancreas. G, Pyloris. K, Kidney. L, Liver. M, Leydig's 

 gland or Epididymis. O, Oesophagus. R, Rectal gland. S, Sperm sac. T, Testis. 

 V, Vesiculae seminalis. W, Wolltian duct. Numbers relate to corresponding parts 

 of the alimentary canal. 



