SUMMAKY OF CURRENT RESEARCHES RELATING TO 



arise secondarily, but by means of the maintenance of intercellular con- 

 nections subsequent to mitotic nuclear divisions : the morphological 

 •continuity is characteristic of the peripheral nervous system. These 

 formations, peripherally as centrally, are to be regarded as neuroblasts. 

 They are the medulla-forming elements. There are no ensheathing 

 so-called Schwann cells. 



Do the elements of the nerve system usually designated as nerve 

 unities {NerveneinheiUri), so far as nerve-cell nets exist, stand in con- 

 tinuous connection ? This question is answered in the affirmative, and 

 the author claims in it a key to the understanding of the morphogeny 

 of the nervous system, from Ccelenterates to man. The neuron theory 

 of to-day is false, and is supported by no observations free from 

 objections. The right understanding of the nervous system, both in 

 ontogenetic and phylogenetic relations, it is claimed, can be arrived at 

 only through the view of central and peripheral neuroblasts originally 

 of equal lvalue, and which change partly into central and peripheral 

 ganglionic and nerve-cells and partly to elements which, through the 

 syncitial structures of the peripheral fibre, yield peripheral nerve-fibre 

 cells. 



Optic Cells of Frog's Eye.* — K. C. Schneider has made some fresh 

 •discoveries in regard to the optic cells in the retina. He describes rod- 

 cells, and notes that the apparently homogeneous axial substance of the 

 rod consists of spiral fibrils with abundant branchings and of a homo- 

 geneous cementing substance. He also deals with the green rod-cells 

 which occur along with the violet-red rods and with the cones. 



Double and Polymorphic Nuclei in Triton.f — W. Rubaschkin 

 describes in the morula of Triton tceniatus the occurrence of double and 

 polymorphic or " mehrblasige " nuclei. These last consist of separate 

 nucleated vesicles which, in most cases, possess a membrane. The 

 form of the nuclei varies according to the number, form, and arrange- 

 ment of the vesicles. The whole complex sometimes has a ring-like 

 form, in other cases a heaping of the elements yields a nucleus of a 

 mulberry form. In the case of double nuclei the two vesicles are of 

 almost identical size, but only one nucleolus is present. It is suggested 

 that the one is a pure descendant of the egg-nucleus and the other of 

 the sperm-nucleus. The author does not attach any important signifi- 

 cance to these unusual phenomena. 



Acidophil Goblet-Cells in Torpedo.f — K. Helly claims that he has 

 found in Selachians the equivalent of the Langerhans islets found in 

 other animals. They are goblet-cells, whose most distinctive character- 

 istic is that their contents are not mucus, but coarse, rounded, light- 

 refracting granules with acidophil reaction. They occur in the stomach, 

 gut, and pancreatic duct of Torpedo marmorata. They appear to be 

 scattered between the epithelial cells, and a definite arrangement is 

 limited only to the deeper crypts. 



* Arbeit. Zool. Inst. Univ. Wien, xvi. (1905) pp. 87-98 (1 pi.). 

 + Arch. Mikr. Anat., lxvi. (1905) pp. 485-500 (1 pi.). 

 \ Tom. cit., pp. 434-9 (1 pi.). 



