ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 537 



After the formation of the third pouch and of the fourth aortic arch 

 behind it, the position of the post-branchial body can be identified at 

 the postero-lateral corner of the pharynx. The pulmonary arch then 

 develops behind this body with an irregular, often double, connection 

 with the dorsal aorta. After the pulmonary arch is complete the fourth 

 pouch appears. The interpretation of the post-branchial body in 

 mammals as a fifth pouch, and of the irregular vessels in front of it as 

 a fifth arch, is not supported by the author's observations. 



Development of Sesamoid Bone.* — 0. Charnock Bradley has in- 

 vestigated the development of the inter-phalangeal sesamoid in several 

 Ungulates and in the rabbit. In all forms examined the flexor tendon 

 is well developed before any indications appear of cartilage in the 

 position ultimately occupied by the sesamoid bone. The development 

 is essentially the same in Ungulates and in the rabbit. The sesamoid is 

 at no period intra-tendinous, but from the first is clearly peri -articular 

 in character. It is probable that this sesamoid represents an ossification 

 in a ligament homologous with the glenoid ligament of the distal inter- 

 phalangeal articulation of man. An interesting point is that in the pig, 

 where the third and fourth digits are the real weight-bearers, the 

 sesamoid is not confined to these, but is present in all the digits. 



Structure and Development of Ovary and Testis of Cat.f — 

 G-. Sainmont has investigated these by the study of a number of 

 embryos. His leading conclusions are that the interstitial cell is a 

 connective cell differentiated like all adipose cells in other connective 

 tissues. It has a trophic role to the epithelial- organs of the ovary and 

 testis, but an internal secretory function is only problematic. The 

 author in a postscript points out a parallelism between the development 

 of this tissue in the testis of the horse (as investigated by Bouin and 

 Ancel) and in the ovary of the cat. 



Development of Sex Structures in Marsupials.^ — A. J. P. van 

 den Broek gives an account of certain phases in the development and 

 relations of the "Wolffian and Mullerian ducts and other related parts as 

 observed in Didelphys, Dasyarus, and Sminthopsis. Some of his points 

 may be noted. The sex cords in the male remain during the whole 

 period of development completely separated. In the female at the time 

 of highest development of the primitive kidney they are separate 

 throughout their extent ; afterwards they unite about the middle of 

 their course at the level of the later developed uterus and its junction 

 with the vagina. The Mullerian duct appears to arise quite indepen- 

 dently and free from the Wolffian. As in other mammals and in man, 

 the germinal gland already shows sexual differentiation before the 

 Mullerian duct is completely developed. The relations of the two 

 ducts to each other are described fully. The course of the ureters is 

 also indicated, and it is noted that in a specimen of Sminthopsis crassi- 

 caudata of 13*2 mm. the ureters opened hypocystically, thus showing a 

 relation to the Wolffian ducts such as persists throughout Life in 



* Anat. Anzeig., xxviii. (1906) pp. 528-36 (5 figs.). 



t Arch, de Biol., xxii. (1906) fasc. 1, pp. 71-161 (6 pis.). 



% Anat. Anzeig., xxviii. (1906) pp. 579-94 (13 figs.). 



Oct. 17th, 1906 2 n 



