92 Swale Vincent and F. D. Thompson, 



sitiou füinis which are figured for diiferent animals by various ob- 

 servers, viz. Maukowski, Laguesse, Dale, and ourselves. 



Rennie's „principal islet" is, we must admit, a very interesting 

 occurrence, and we have verified its frequent presence in quite diffe- 

 rent species from those examined by this author. But we cannot 

 admit that it carries the significance attached to it by Rennie. The fact 

 that the teleostean islets are so often encapsuled loses much of its 

 importance when it is pointed out that isolated portions of the zymo- 

 genous tissue are also frequently encapsuled. 



Lewaschew ^), as the result of injection experiments, found in some 

 cases lumina in the islets of mammals. Dogiel^), on the other hand, 

 using Golgi's silver Chromate impregnation, was unable to confirm this, 

 and explained Lewaschew's results as due to extravasation of the in- 

 jected material. But Laguesse, using the same method, found in the 

 islets of the snake, lumina in perfect continuity with those of the acini 

 and his plates show an admirable figure illustrating this. He considers, 

 in fact, that in reptiles there are strictly speaking no solid cords at 

 all, but only columns of cells in which the lumen has become effaced. 

 In Kinosternon in some of the leptochrome islets we have been able 

 to find distinct lumina, but so far have not traced their connections 

 with the lumina of the acini (see PI. V, fig. 12. I.). In Amia calva 

 too we have described lumina in the islet (V. supra p. 21). 



We have described and depicted what appear to be two kinds of 

 tissue in the vertebrate pancreas, over and above the zymogenous 

 secreting tubules. In birds, reptiles, and amphibians the two kinds 

 of structure ai*e very obvious, while in mammals and fishes the one 

 kind (the bathychrome tissue) is in small amount and scattered. We 

 have suggested that these (which we have named respectively the 

 leptochrome and bathychrome tissues) may correspond to Laguesse's 

 primary and secondary islets.") 



With regard to the two kinds of leptochrome islet the „alveolar" 



') Loc. cil. 



^ Arch. f. Anuf. u. I'hysiol. S. 121. 18»:;. 



■'') 'I'liis seems mori! douhllul to us now lliaii wlnii the aliove was wiiHeii. 

 [Note a.lde.l .1,111. I. 1!K)7.| 



