386 SUMMARY OF CURRENT RESEARCHES RELATING TO 



SUMMAKY 



OF CURRENT RESEARCHES RELATING TO 



ZOOLOGY AND BOTANY 



(principally Invertebrata and Cryptogamia), 



MICROSCOPY, &c, 



INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS. 1 



ZOOLOGY. 



A. VERTEBRATA :— Embryology, Histology, and General. 



a. Embryology.t 



Spermatogenesis of Marsupials, f — Dr. C. M. Fiirst has had the 

 rare opportunity of studying the spermatogenesis of marsupials. The 

 testes which he has sectioned were those of Metachirus quica and 

 Phascogale albipes. His chief results are as follows : — 



The seminal canals contain two main forms of cell — the seminal 

 and the marginal cells. The latter have no direct role in spermato- 

 genesis. The former exhibit three stages — (a) the primitive cells (S 2 ) 

 (Samenstammzellen), which give origin by division to (6) the sperm- 

 mother-cells (S 1 ) (Samenmutterzellen), which divide by karyokinesis to 

 form (c) the sperm-daughter-cells (Samentochterzellen (S°), which give 

 off a polar body and form spermatozoa (S). The first are peripheral, 

 the second move centre wards, the third are median and central. The 

 cells and spermatozoa lie in tiers and rows, each of which exhibits cells 

 of the same stage. Development proceeds from the periphery inwards, 

 and a complete series may be observed in successftil sections. In the 

 sperm-daughter-cells (S°) the nucleus undergoes polar differentiation, a 

 cap is formed, a polar body is extruded at the tail end (opposite to the 

 cap), then maturation proceeds apace. 



The nucleus elongates and grows. The diffusely stained contents 

 exhibit well-defined chromatin-granules. These aggregate along with 

 adjacent achromatin and are drawn to the cap. The nuclear membrane 

 is invaginated. The chromatin is disposed at the cap and tail poles. 

 The cap becomes flat and is finally thrown off. The chromatin nuclear 

 substance, continuous with that of the head, is prolonged in a fine thread 

 at the tail end. The cellular substance is lost. Nuclear substance alone 

 is left ; a spiral thread occurs only provisionally. The sperm consists of 



* The Society are not intended to be denoted by the editorial " we," and they do 

 not hold themselves responsible for the views of the authors of the papers noted, 

 nor for any claim to novelty or otherwise made by them. The object of this part of 

 the Journal is to present a summary of the papers as actually published, and to 

 describe and illustrate Instruments, Apparatus, &c, which are either new or have 

 not been previously described in this country. 



t This section includes not only papers relating to Embryology properly so called, 

 but also those dealing with Evolution, Development, and Reproduction, and allied 

 subjects. 



% Arch. f. Mikr. Atiat., xxx. (1887) pp. 336-65 (3 pis.)- 



