182 SUMMARY OF CUEEENT EESEAECHES EELATING TO 



Early Development of Peripheral Nerves in Vertebrate Embryo. 

 — H. H. Lane {Proc. Amer. Soc. Zool iu Anat. Record, 1920, 17,324). 

 The chief nerve trunks are laid down before distinctly nervous functions 

 can be present. In the rat embryo of 23 mm. in length the vestibular 

 and cochlear nerves are well developed, though there is no hearing until 

 about the twelfth day after birth ; in the 16 mm. embryo the vibrissa 

 have not emerged, yet the maxillaris and mandibularis branches of the 

 trigeminus are well formed. According to Harrison's experiments on 

 the cultivation of tissues in vitro, each neurone sends out its axone in a 

 predetermined manner and direction to a distance of a millimetre or so, 

 enough to reach at an early stage, but only at an early stage, to the 

 part it is destined to innervate. J. A. T. 



Branchial Segmentation of Cranial Nerves. — K Betchov {Revue 

 Suisse Zool., 1918, 26, 233-44, 2 figs.). It is a common usage to 

 refer the trigeminal to the first branchial arch, the facial to the second, 

 the glosso-pharyngeal to the third, and the vago-spinal to the remainder. 

 The author indicates some of the difficulties in this interpretation and 

 proposes another. The trigeminal is the nerve of the buccal cleft. 

 The acustico-facial is associated with the first branchial cleft, the glosso- 

 pharyngeal with the second, the superior laryngeal with the third, the 

 recurrent spinal with the sixth. The fourth and fifth clefts no longer 

 possess special innervation. Hia interpretation appHes directly to 

 mammals. J. A. T. 



Development of Pancreas. — Aeox (C R. Soc. Biol., 1919, 82, 

 1428-30). A study of the pancreas in embryos of the pig goes to show 

 that the endocrinal gland appears somewhat late in the course of 

 development, and suggests that the embryonic pancreas may have an 

 erythropoietic function, like the embryonic liver, but more restricted 

 and more accessory. J. A. T. 



Development of Thymus, Parathyroid and Ultimo-branchial Bodies 

 in Turtles. — C. E. Johnson {Proc. Amer. Soc. Zool. in Anat. Record, 

 1920, 17, 325-6). In embryos of Ghelydra, Ghrysemis, Triomjx the 

 thymus arises from the third and fifth visceral pouches. The third 

 also gives rise to a parathyroid body ; this is not the case, at least as 

 a rule, with the fifth. The ultimo-branchial body arises as a secondary 

 diverticulum from an evagination from the pharynx, which also gives 

 origin to the fourth and lifth visceral pouches. The ultimo-branchial 

 body is relatively very large, especially in Ghelydra ; it is at first nearly 

 equal on the two sides, but that on the right soon lags, and, as a rule, 

 attains only relatively small size. J. A. T. 



Influence on Frog's Inter-renal Tissue of Extirpation of the 

 Thyroid and Pituitary Primordia. — Alice L. Brown {Proc. Amer. 

 Soc. Zool. in Anat. Record, 1920, 17, 326). In larvje of Rana pipiens 

 twenty-seven months old, from which the thyroid primordia had been 

 removed, the inter-renal tissue remained as irregular, but definite tissue 

 masses about the renal vein. In larvae, from which the pituitary pri- 

 mordium had been removed, the inter-renal tissue was smaller and less 



