Misce lla neous. 511 



of very distinct upper incisors, giving them the formula I. i, C. i, 

 M. 1^. According to M. Paul Gervais these last when young have 

 two pairs of upper incisors, one of which has disappeared in the 

 adult ; the young animals would have the formula I. |, C. i, M. ^. 

 M. Gervais does not doubt that at a still earlier age a third pair 

 of upper incisors might be found in these animals, the dental for- 

 mula of which would then be the same as that of the Pachyderms, 

 less one molar, viz. I. |-, C. j-, M. f . 



The Biuotheria and Amphitraguli, the latter regarded as Rumi- 

 nants allied to the ehevrotains, have seven molars — that is to say, the 

 same number as the Pachyderms. Thus among the Ruminants 

 fossil species were already known having the same dental formula 

 as the Pachyderms, and living species of which the formula was 

 almost identical ; and Goodsir's discovery, giving the ordinary Ru- 

 minants at a certain age the same formula as the Pachyderms, 

 enabled the two groups to be approximated. Here was one of the 

 results of the hj-pothesis of the unity of plan in nature, or a con- 

 firmation of the transformist theory, the abortion of the organs being 

 exjjlained by their disuse and the gradual establishment of this 

 anomaly by adaptation and heredity. 



The author says that, wishing to verify an opinion which en- 

 joyed so much credit in science, he was surprised to find nothing 

 to justify it. In a long series of preparations from embryos of 

 cattle and sheep, from the earliest period of embryonic life up to 

 the time when the foetus is 30 centims. long in the sheep, he 

 was never able to ascertain the presence of follicles, nor even of 

 any trace of the epithelial lamina, the commencement of all follicular 

 development. 



Goodsir's error arose from the false idea he entertained of the 

 development of the follicles ; and, in fact, at the commencement of 

 his researches, the author fell into the same error himself. In sec- 

 tions made quite at the anterior part of the upper jaw in the ox 

 and sheep, there is on each side of the median line an epithelial 

 sac which separates from the mucous membrane of the mouth to 

 bury itself in the jaw. The mucous layer of Malpighi, uninter- 

 rupted, forms its outer covering ; whilst in its interior there is a 

 polyhedral epithelium in every respect like that of the middle layers 

 of the buccal epithelium. Thus formed, this little sac would seem 

 to constitute the commencement of the follicle ; but by making 

 sections of the same jaw further and further from the front, the 

 little sac is seen to lose its relations with the buccal mucous mem- 

 brane, and ac(juires the form of a circular canal, approximating to 

 the mucous membrance of the nasal fossae. 8oon a cartilaginous 

 tube appears round this canal ; and then a ridge containing vessels 

 is formed at its upper part. It is Jacobson's organ as described by 

 Gratiolct. — Comptes liendus, March 12, 1877, p. 508. 



