38o SCIENCE PROGRESS 



(first, second, third), and six post-otic." The fourth breaks 

 down completely into mesenchyme. The fifth forms muscle- 

 fibres but later breaks down. The sixth, seventh, eighth, and 

 ninth produce permanent myotomes. " The tenth somite 

 (first of the trunk, and second post-vagal), corresponds to the 

 first mixed nerve." 



The development of the pharyngeal derivatives in the calf 

 (Bos tauriis) is described by E. L. Anderson in the Anat. 

 Rec.y vol. xxiv. No. i, Aug. 1922. The chief peculiarity in 

 development occurs in the parathyroids. These appear as 

 proliferations of the epithelium of the pouches, adjacent to the 

 corresponding aortic arches, and are highly vascular from the 

 first. 



E. Giglio-Tos, in the first of a series of studies in develop- 

 mental mechanisms, gives a very full account of the processes 

 involved in the early segmentation of the egg of the sea urchin 

 {Archiv fur Entwick. der Organ., July 1922). In the same 

 journal A. Lipschiitz, B. Ottow, and K. Wagner describe cases 

 of sterility in rabbits resulting from under-development of the 

 testes, the result of removing a part of that organ during 

 development, and at the same time cutting through the ductus 

 epididymis. 



Invertebrate Morphology. — A paper " On the Septal and 

 Pharyngeal Glands of the Microdrili (Oligochaeta) " is contri- 

 buted by J. Stephenson to the Trans. R.S. Ed., vol. liii. Part I, 

 No. 12. He points out that the chromophil cells in the Micro- 

 drili, as in the earthworms, have no direct connection by means 

 of long-drawn-out necks with the alimentary epithelium. 

 They therefore constitute " ductless glands," and their secretion 

 (largely disintegration products) is an " internal secretion, 

 which, in most cases, mixes with the coelomic fluid." 



The condition of the septal glands of Enchytraeids is com- 

 parable with that in earthworms. The secretion in both cases 

 reaches the pharyngeal lumen by percolation, in the former 

 down strands of non-staining tissue, and in the latter through 

 the felt of muscular fibres. 



The chromophil cells are believed to arise from the peritoneal 

 lining of the coelomic cavity, and are therefore mesoblastic 

 in origin. 



In a paper on " The Infra-cerebral Organs of Peripatus " 

 {Q.J. M.S., vol. Ixvi, Part III, Sept. 1922), W. J. Dakin suggests 

 that the infra-cerebral vesicles of this animal are homologous 

 with the cephalic pits of other Tracheate embryos. In the 

 latter the pits become closed off, the walls become parts of the 

 cerebral ganglion, and the cavities disappear altogether. In 

 Peripatus, on the other hand, the vesicles remain, but they 

 are graduallj'- constricted off from the rest of the supra- 



