348 



A. Ärnbäck Christie-Linde 



in about the same way as in Sorex and Neomys — which opens 

 behind. Besides, the organ itself is not so large as in the younger 

 individuals. 



Judging from tbis oldcr individnal examined, it is probable that 

 the cartilaginous outer bar, representing a rudinientary turbinal, is 

 to be found only in early stages of Crocidura russula and that it 

 very soon disappears in the course of development. 



Fi*. 5. 



Fig. 6. 



Id. 



n.f.c- 



pmx. 

 n.p.c 



' — * 



J 



pmx. 



Tupaja sp. Foetus (44 mm). Transverse sections ofregion of Jacobson's organ. a.n. alinasal cartilage; 

 c.p. cartilago palatina; c.ps. cartilago paraseptalis; J.o. Jacobson's organ; l.d. lachrymal duct; 

 n.f.c. nasal floor cartilage; n.p.c. naso-palatine canal; n.s. nasal septum; pmx. premaxillary ; v. Dlood- 



vessel. x c. 4S. 



When comparing the foetal shrews examined: Crocidura russula, 

 Sorex araneus and Neomys fodiens, we find that in the two latter 

 the organ of Jacobson is of a less conaplicated type than in Croci- 

 dura russula, and tbis is true of the cartilaginous parts as well as 

 of the organ itself. 



The most striking point of difference is, however, the presence 

 of a cartilaginous bar on the outer side of its forernost part in the 

 last-mentioned species. This small cartilage and the considerable 

 size of the organ itself give to the organ in Crocidura a more primi- 

 tive character. 



