"24<i DR K. BROOM ON THE 



hi tracing the affinities between this type and that of the Marsupials we have at first 

 a slight difficulty. With regard to the main body of the organ and its cartilaginous cap- 

 sule the agreement between the two is close, but as we pass to the front the differences 

 become more marked. The organ has a fairly long distinct duct, and even after it opens 

 into the upper part of the naso-palatine canal it preserves for a short distance its indivi- 

 duality as a distinct groove. One of the main characteristics of the Miniopterus type, 

 and of the higher Eutherian type generally, is due to this anterior extension of the duct 

 of Jacobson being supported by an anterior process from the cartilage of Jacobson. Then, 

 again, the outer part of the nasal floor cartilage is much better developed than in the 

 Marsupials, and in some respects it has more resemblance to the Monotreme type, espe- 

 cially where the posterior part becomes well developed and passes in below the organ 

 of Jacobson. The great development, however, of the outer part of the nasal floor carti- 

 lage gives rise in front to a special process passing forward on the outer side of the naso- 

 palatine canal. The anterior process of Jacobson 's cartilage, and that from the outer 

 nasal floor cartilage, unite in front by their upper edges, the united cartilages forming 

 the support to the upper part of the naso-palatine canal. Though there is no similar 

 development in Marsupials, there is frequently present in Diprotodonts a downward pro- 

 cess of Jacobson \s cartilage by the side of the naso-palatine canal, which is apparently a 

 rudimentary homologue of the anterior process in Miniopterus and the higher Eutheria. 

 Different modifications of this downward development of Jacobson's cartilage are found 

 in Perameles, Trichosurus, Phascolarctus, Macropus, and Phascolomys. The posterior 

 and anterior developments of the outer nasal floor cartilage are no doubt homologous 

 with the outer nasal floor cartilage and its anterior process in the rabbit, but whether the 

 rodent condition represents a degeneration from the elaborate arrangement found in the 

 higher Eutheria, or a pure parallel development, it is difficult to decide definitely, though 

 the latter alternative appears the more likely. 



Lemuridse. — I have not had an opportunity of examining personally any member of 

 this group, but fortunately Herzfeld has made an examination of the organ and its carti- 

 lages in Lemur, and so far as he has figured his sections the type followed differs in no 

 essentials from that of Miniopterus. 



Insectivora. — The organ in members of the Insectivora has been examined by HarvEY 

 and Herzfeld, while Parker in his monograph on the development of the skull gives 

 numerous figures of sections through the organ. Parker's figures, however, are on too 

 small a scale to give more than rough indications of the arrangements. Harvey has 

 noted the general features in the hedgehog, and Herzfeld has figured the organ in the 

 mole, though this latter animal is a much less satisfactory insectivorous type than the 

 former. 



Taking the hedgehog as the insectivorous type, we find in it an organ which differs 

 but little from that of the bat, except that in a few points there are indications of a more 

 advanced stage of organisation. As in the majority of the higher Eutheria the naso- 

 palatine canal is long, and passes very obliquely upwards and backwards, and the great 



