ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 9 



appears late in the development of the salmon, and is associated with 

 the rotation of the glenoid border into a transversely horizontal position. 

 There is no sign of a mesocoracoid during development in the stickle- 

 back, and this is associated with the rotation of the glenoid border into 

 a vertical position. Those Teleosts without a mesocoracoid probably 

 constitute a group separate and not originating from those Teleosts with 

 a mesocoracoid. The postcoracoid process, which is so prominent a 

 feature during development, represents the metapterygium. The so- 

 called " interclavicle " of the stickleback is not part of the coracoid, but 

 arises as a separate dermal ossification. It is not homologous with the 

 bone of the same name in the sturgeon, and should therefore receive a 

 different name, e.g. infracleithrum. 



Development of Lymphatic System in Tadpoles.* — H. Hoyer gives 

 an account of the development of the lymph-vessels and lymph hearts 

 in the frog, and points out the probability that in all Vertebrates the 

 primordium of this system is paired and symmetrical. 



b. Histoloery. 



Resting Nuclei and Mitosis.f — K. v. Tellyesniczky has investigated 

 the condition of the resting nucleus and the origin and changes of the 

 nuclear threads, making use of spermatogonia of the salamander. The 

 only constant element of the living nucleus is the nuclear fluid — the 

 ground substance of the " fixed " nucleus. It is homogeneous, but in 

 " fallenden Fixationen " it appears as granules and masses. In the 

 nuclear fluid are two kinds of corpuscles, nucleoli and karyosomes ; 

 these form no constituent of casual structures. There is no justification 

 for the theories which speak of " linin, paralinin, oedematin, pyrenin, etc." 

 These terms lead but to misconceptions, and should be avoided. The 

 karyosomes and nucleoli differ in form, substance, development, and 

 behaviour. The substance of the karyosomes is in agreement with the 

 idea of " chromatin," that of the nucleoli is in genetic relationship to fat- 

 stuffs. The most important phenomenon at the beginning of mitosis 

 is the diffuse distribution of all the corpuscles present. The nucleoli 

 disappear by gradual diminution in size and without special phenomena. 

 The karyosomes first broaden out, then become branched and vacuolated, 

 and subsequently vanish. In both kinds of division the thread arises as 

 a new formation, and takes its origin in a highly delicate and intricate 

 manner from the diffusely distributed nuclear substance in the nuclear 

 fluid. Eeduction divisions are probably distinctive in character ; the 

 threads are not so smooth, nor so sharply defined as in ordinary divisions. 

 Various other points are discussed in this very full paper. 



Peripheral Nervous System in Amphibian Larvse.| — 0. Schultze 

 has amongst other points investigated the history of the axis cylinder 

 of the peripheral nerve fibre. He finds that the embryonic non- 

 medullate sensory fibre is nothing else than a multiplicity of cells — a 

 syncitium arising from typical neuroblasts. This syncitium does not 



* Bull. Internat. Acad. Sci. Cracovie, 1905, pp. 417-30 (3 figs.). 

 t Arch. Mikr. Anat., lxvi. (1905) pp. 367-433 (5 pis.). 

 % Tom. cit., pp. 41-110 (4 pis.). 



