ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 371 



b. Histolog-y. 



Discession of Cliromosomes and Mitokinetism.* — Marcus Hartog 

 has previously sought to show that the phenomena of the cell-spindle 

 may be interpreted as the expression of a field of dual force, centring 

 on the centrosomes as opposite poles, on the assumption that the 

 achromatic fibres are more permeable to the force than their sur- 

 roundings, and lie along the lines of force whose distribution they, of 

 course, modify. The chromosomes are also more permeable, and may 

 be termed " flexible inductors." Further experimentation has led him 

 to a view which explains the discession of the chromosomes in 

 congruence with the theory outlined. 



Comparative Study of Vermiform Appendix.f — W. C. Mackenzie 

 finds that man, ape, wombat, and Echidna have a true vermiform 

 appendix. Various grades of degeneration of the appendix of Echidna 

 occur. In the wombat it may entirely disappear, by incorporation in 

 the wall of the ileum. In Omithorhynchus there is a crecum. 



Spleen of Carnivores. | — Ed. Retterer and H. Neuville have 

 investigated the structure of the spleen in various Carnivora. In the 

 bear and the liou there is a syncytium surrounding the splenic 

 arterioles, not a reticulum with meshes containing free lymphocytes. 

 This syncytium represents the first stage in the evolution of the splenic 

 parenchyma. It is traversed by granular anastomosing filaments, and 

 not by collagenous or connective filjres. The syncytium represents 

 germinative centres, and is transformed into reticulate tissue with 

 empty meshes. By the disintegration of the reticulum the cellular 

 remains become free as leucocytes, and if the nucleus has undergone 

 hasmoglobic-degeneration it becomes a red blood-corpuscle. 



Spleen of Cetaceans. § — Ed. Retterer and H. Neuville give an 

 account of the structure of the spleen in some Delphinida? (dolphin, 

 porpoise, Orca gladiator and Grampus griseus). In relation to the rest 

 of the body the spleen is small. The splenic mass is divided in multiple 

 lobes whicii are quite distinct. It is not merely that there are incisions, 

 as in many Mammals ; each lobe is enveloped in a distinct connective 

 muscular tunic. 



Minute Structure of the Spleen. || — Ed. Retterer has studied the 

 vascular reticulum of the spleen in various types of Mammals. After 

 passing into lacuna; without proper walls, the splenic arterioles continued 

 into canals (venous radicles) whose reticulate wall is formed of stellate 

 splenic cells, disposed concentrically to the lumen. The vascular 

 reticulum of the spleen is identical, as regards origin and structure, 

 with the sinuses and lacunse of lymphatic ganglia. 



* Rep. Brit. Assoc. Manchester, 1916, pp. 470-1. 



t Rep. Brit. Assoc. Manchester, 1916, p. 472. 



X C.R. Soc. Biol. Paris, Ixxviii. (1916) pp. 557-61. 



§ C.R. Soc. Biol. Paris, Ixxix. (1916) pp. 60-4. 



li C.R. Soc. Biol. Paris, Ixxix. (1916) pp. 124-8. 



