On the Relations between the „Islets of Langerhans" etc. 73 



For some time we were of opinion that this batliychrome tissue 

 represented the only structures present in the reptilian pancreas, in 

 addition to the secreting alveoli. But our observations in birds led 

 us to look at our slides more carefully and as a result we have found 

 in Kinosternon a few leptochrome islets of the type we were familiar 

 with in various groups of vertebrates. These islets are visible under 

 the low power of the microscope as faintly staining, rather ill-defined 

 patches, having an abundant capillary supply (PI. V, fig. 12, lejjt. t., i.). 

 In our specimens we confess, these leptochrome islets are rare, but 

 there can be no doubt of their actual existence. Their occurrence 

 in birds would tend very strongly to make one anticipate their presence 

 in reptiles, and we feel sure that they might be commonly found In 

 some other types. Moreover, Diamare has depicted a good example 

 of such an islet in Lacerta. 



We have been unable to find any distinct leptochrome islets in 

 Chrysemys pietà. This may possibly be due to the fact that the 

 animal was killed at the beginning of the winter, when it had recently 

 put itself into a state of full nutrition for the period of hibernation. 

 In Chrysemys there are however bathychrome columns having the same 

 structure as in Kinosternon. There are, moreover, here and there 

 throughout the section, examples of individual bathychrome cells. 



In our two reptiles also we find masses of adenoid tissue invading 

 the pancreas and small clumps of tissue resembling spleen, as de- 

 scribed by other observers (PI. V, fig. 12, ad?). 



Thus in Reptiles as in Birds and to a less extent in mammals, we 

 have two distinct kinds of tissue over and above the zymogenous tubules, 

 viz. the bathychrome and the leptochrome. It is probable, although 

 we have at present no experimental proof of this, that it is only the 

 leptochrome islets in these animals which unlergo transformations in 

 different physiological conditions. 



In some of the islets, we find, as did Laguesse, distinct lumina 

 within the limits of the islet, which limits are indicated by the diffe- 

 rence in staining reaction and capillary blood supply and other features 

 already fully described (PI. V, fig. 12, I). 



