INTESTINAL CANAL OF THE ICHTHTOPSIDA. 399 



tion of this gland * and that of the " anal or circutn-anal glands 

 of many higher animals ; " and he accordingly proposes to term 

 it the '"'' glandula superanalis " (/. c. p. 182). To English students 

 this structure is best known as the "rectal gland." Blanchard's 

 researches seem to point to its origin as an outgrowth of the 

 hypoblastic gut ; those structures which we commonly term 

 " rectal " or " anal " glands, are associated with the terminal 

 epidermal portion of the hind gut, and it is tolerably safe to 

 conclude that from this they are developed. Proof that this is 

 so does not appear to be at present forthcoming ; but the facts 

 to which I have alluded warrant the withdrawal of the term 

 " rectal gland " in the case of the Plagiostomi. 



The appendix digitiformis has been by Hyrtl regarded (18. 

 pp. 28-29) as accessory to the reproductive apparatus rather 

 than to the alimentary. He based his assumption f upon the 

 failure to find food-stuff within it, and upon a belief in its 

 increase in size in animals whose oviducts contained eggs. I 

 have examined a series of specimens of Raia and Mustelus having 

 eggs and young in their oviducts, in vain, for confirmation of 

 Hyrtl's belief ; and confidence in the same is further shaken by 

 the fact that his views fail to explain the presence of the organ 

 in the male in a form indistinguishable from that of the female. 

 Moreover, the course taken by its duct, and the fact that its 

 secretion is discharged well forwards into the intestine, would 

 appear to be irreconcilable with this view. In the fact that this 

 organ is a secretory one, we have, in the long run, a further 

 point of agreement with the caecum coli and appendix vermi- 

 formis. The fact that the latter becomes an adenoid in its most 

 highly differentiated form, while the processus digitiformis is not 

 known to be thus constituted +, would appear to be of minor 

 significance, by analogy with Weldon's discovery (32. p. 176) that 



* On p. 181 of his pamphlet, Blanchard attributes to Milne-Edwards 

 (Anat. et Phys. Comp. t. vii. pp. 326, 332) the belief that this structure 

 represents "a special urinary bladder." M. Milne-Edwards makes (" in seinem 

 trefflichen Lehrbuch " [Blancbard, I. c.]) no such statement ; he "alludes not to 

 the appendix digitiformis, but to the well-known urinary receptacle, which I 

 have elsewhere proposed to term the Wolffian bladder (Journ. Anat. & Phys. 

 vol. xxiv. [n. s. vol. iv.] p. 408, 1890). 



t Blanchard (1. c.) appears to have been unaware of this. 



X Migratory leucocytes have been observed in the " cloacal epithelium " of 

 Raia, Torpedo, and Sqicatina (List, J. H., " Studien an Epithelien," Archiv f. 

 mikr. Anat. Bd. xxv. pp. 2fi4-268, 188.5). 



28* 



