78 ARKIV FÖR ZOOLOGI. BAND 1. 



Another school again, not believing in the inheritance of ac- 

 quired characteristics wouldgive the following explanation. The 

 variation goes in every direction. Soine lizards develop blunter 

 teeth than others. These then get an increased faculty of 

 crnshing the shells of land-molluscs, which offer themselves 

 as a nourishing and at the same tirae easily accessible prey. 

 The variation in such a direction is favonrable and has thns 

 greater possibilities to snrvive, other types of variation being 

 less fortunate under the same circumstances and therefore 

 doomed to extermination. 



Whether one way of explanation or the other is chosen 

 and accepted the indisputable fact remains that we have 

 here one of the most remarkable adaptations to a certain diet. 



Although the main purpose with this paper was to de- 

 liver the above description and point out the characteristie 

 features of the skull in connection with the changed feeding" 

 habits of the lizard, I think some notes about the intestinal 

 canal may not seem uncalled for, the less so as they com- 

 plement the investigations I have made before concerning the 

 intestinal canal of the lizards, about which, on the whole the 

 scientific knowledge needs to be greatly increased. The ven- 

 tricle of V. niloticus is, at the cardia, strongly constricted 

 and may be said to be quite closed off from the oesophagus which 

 is laid into strong longitudinal folds. The shape of the ven- 

 tricle is that of an irregular and thick spindle the left side 

 being much more convex, than the right, which is almost 

 straight. In such a way to certain extent a fundus is formed 

 and curvatura major and minor may be traced. The car- 

 dia-portion is more suddenly constricted. Posteriorly the ven- 

 tricle is more gradually narrowed at the same ti me as its 

 muscular coat is highly thickened. The posterior end is curved 

 towards the median line about 1 l / 2 cm - from the sphinc- 

 ter and beyond this follows that pyloric tract which I 

 have found and described in my previous paper* on the in- 

 testinal canal of lizards. This pylorictract is transversely 

 directed as a continuation of the recurved end of the muscu- 

 lar ventricle. To give an idea of the proportions of the 



* On some points of relation between the niorphological structure of the 

 intestine and the diet of Reptiles. Bih. K. Vet Akad. Handl. Bd. 28. Stock- 

 holm 1902. 



