ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 489 



Growth in Weight of White Mice.* — M. Stefanowska has plotted 

 out curves for both sexes, and finds four main periods. There is first a 

 period of slow increase until the 16th day. Then follows a long 

 period of maximum rate of increase from the 10th to the 45th day. 

 The third period, from the 45th to the 67th day, corresponding to the 

 advent of puberty, is especially marked by its irregular course, a descent, 

 a rise, and an arrest. In the fourth period, from the 67th day until 

 mature size (91st day) the growth proceeds again slowly. There is a 

 close parallelism in the curves for the two sexes. 



Vascular System of Amphioxus.f — R. Legros has filled some of 

 the many gaps in our knowledge of the vascular system in this type. 

 He gives a detailed account of the vessels, and does not find any evidence 

 to support the view that the vascular system communicates with any 

 truly coelomic space. The vessels are definitely closed by a continuous 

 endothelial lining. 



Legros directs particular attention, in addition to his discovery of a 

 trapeze muscle on the right side, to the parietal coelomic canals which 

 connect the sub-chordal ccelom of the branchial region with the peri- 

 gonadial coelomic cavities, and to the ascending visceral branch of certain 

 dorsal nerves (27th-31st). 



Tunicata. 



Function of Ganglion in Ciona intestinalis.J — R.Magnus has 

 experimented on this favourable subject for testing the function of the 

 Tunicate's central nervous system. The system is reduced, as is well 

 known, to a single ganglion from which the musculature of the body- 

 wall is innervated. There is but one characteristic reflex, namely, a 

 closing of the apertures and a retraction of the whole animal if one of 

 the syphons is touched. Loeb has maintained that this reflex persists 

 after the ganglion has been extirpated, and supposes a propagation of 

 the stimulus from muscle-cell to muscle-cell. 



Magnus finds, however, that extirpation of the ganglion puts an end 

 (for the time being) to the reflex, and leaves only local reactions possible. 

 After extirpation there is no transmission of stimulus from one side of 

 the body to another, or from one syphon to another. Only local 

 reactions occur. 



After two or three weeks, however, the original reflex may suddenly 

 reappear, and then it is found that the ganglion has been regenerated. 

 There is no warrant for supposing that there is a transmission of 

 stimulus from muscle-fibre to muscle-fibre. The ganglion is a true and 

 indispensable reflex-centre. 



Digestive Glands of Monascidise^ — A. Isert describes in detail 

 the structure of the main digestive gland in a number of solitary 

 ascidians. The organ is most developed in Microcosrnidaa, Cynthiae, 

 and Molgulidas, where it is a distinctly visible organ in direct connection 

 with the stomach. In other forms there is rather a glandular region 



-'&■ 



* Comptes Kendus, cxxxvi. (1903) pp. 1090-3. 



t M.T. Zool. Stat. Neapel, xv. (1902) pp. 487-554 (4 pis.). 



% Tom. cit., pp. 483-6 (1 fig.). 



§ Arch. f. Naturges., lxix. (1903) pp. 237-96 (4 pis.). 



