36 SUMMARY OF CURRENT RESEARCHES RELATING TO 



polariscope. The main conclusion is that in all striped muscle the 

 strise represent sarcoplasma, a layer of which surrounds every fibril. 



The second part of the paper gives a glance over what Eollett calls 

 the " Muskelromantik," whose pages, he says, vie with fiction in their 

 strangeness. He deprecates the withholding of criticism, and proceeds 

 to a vigorous criticism of the network theory of muscle structure. 

 Melland, Marshall, and van Gehuchten occupy a prominent place, and 

 Eamon y Cajal, Carnoy, and Macallum have also their share. The 

 existence of a network is denied in toto, except in so far as it represents 

 the edges of EoUett's walls of sarcoplasma. 



Striicture of Spermatozoa.* — Herr E. Ballowitz communicates the 

 results of his investigation of the minute structure of spermatozoa. He 

 deals first with the general characters of bird spermatozoa. No less 

 than forty-two species were examined. The spermatozoa of Passeres are 

 made the subject of special discussion ; — the structure of the lash, the 

 development of the spiral fringe from the protoplasm of the spermatide, 

 and the structure of the head are described in minute detail. In a 

 second chapter the author similarly describes the spermatozoa of Na- 

 tatores, Grallatores, Gallinacei, Columbinte, Scansores, Kaptatores, and 

 Cajprimulgus europseus. The fibrillar structure of the axial filament is 

 especially emphasized. The movements of the sperms are also de- 

 scribed. It may be concluded with certainty that the axial filament is 

 the essential part of the lash and the definite seat of the contractility. 

 The fibrillar structure, demonstrated by the author, is in the closest 

 association with this contractility. It will be afterwards shown that 

 other portions of the lash acquire a fine fibrillar structure when they 

 become contractile. 



Club-shaped Nucleoli.! — Herr S. M. Lukjanow describes peculiar 

 club-shaped nucleoli from the mucous membrane of the stomach of the 

 salamander. They appear, however, to be of wide occurrence. The 

 author's study of these structures led him to regard them as stages pre- 

 paratory to an emptying of the contents of the nucleolus. He also 

 connects what he observed with phenomena of nucleolar movement. 



Nervous System of Amphioxus.| — Dr. E. Eohde reports the result 

 of his histological observations on the nervous system oi Amphioxus. The 

 present memoir is in part a continuation of the author's investigation of the 

 connection between the ganglion-cells and nerve-fibres in Chaetopods. A 

 brief summary of the general morphological facts is first given. The central 

 nerve-strand has its largest diameter in the middle of the body ; there 

 are no swellings of any kind ; the central canal is usually narrow in its 

 larger dorsal portion ; the anterior expansion is histologically distin- 

 guishable as a cerebral region. The central canal is surrounded by a 

 usually simple layer of epithelial cells ; the nervous elements consist of 

 an internal ganglionic layer and a much larger external fibrous layer. 

 From the dorsal portion 64 pairs of sensory nerves are given off, en- 

 sheathed at their origin by the connective tissue swathing the nerve- 

 strand. They pass to the muscle-ligaments and to the skin. Entering 

 the ligament the nerve divides into a ventral and a usually weaker 

 dorsal branch. From the ventral side of the central system, alternating 



* Arch. f. Mikr. Anat., xxxii. (1888) pp. 401-73 (5 pis.). 



t T. c, pp. 474-8 (1 pi.). 



I Zool. Beitr. (Schneider), ii. (1888) pp. 169-211 (2 pis.). 



