20 First 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 in 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, Wollfian duct. Numbers relate to corresponding parts 
of the alimentary canal. 
