SUMMAEY OF CURRENT RESEARCHES 



RELATING TO 



ZOOLOGY AND BOTANY 



(principally invertebrata and cryptogamia), 



MICROSCOPY, Etc.* 



ZOOLOGY. 



VEKTEBRATA. 

 a. Embryology, f 



Development of Gonads of Fvog.%— E. Witschi begins with the 

 " indifferent " stage. A single layer of germinal epithelium bounds a 

 central cavity, the primitive genital cavity. Into this from the suspen- 

 sory band there project solid partitions at regular intervals. These are 

 the sex-strands of the pronephros. 



Characteristic of the development of the ovary is the peripheral 

 germinal epithelium and the early passage of the germ-cells into the 

 growing phase. Characteristic of the direct development of the testes 

 is the central position of the germ-forming areas (the urogenital con- 

 nexion), and the late onset of the growing phase in the germ-cells. But 

 in most cases (perhaps in all cases in natural conditions) the testes arise 

 indirectly from an indifferent stage, which first puts on the characteristics 

 of an ovary. The germinal epithelium thickens ; nests of ova are 

 formed ; the elements pass through a phase of pseudo-reduction ; sooner 

 or later multiplying cells or strands of these separate from the germinal 

 epithelium and migrate into the sex-strands ; and, as in direct develop- 

 ment, a typical testis is formed in the centre with seminal canaliculi 

 and a rete. 



The germ-cells of the indifferent stage arise from cells which lie at 

 first outside the region of the subsequent gonads, and preserve the 

 character of undifferentiated embryonic cells until they undergo meta- 

 morphosis into typical germ-cells. According to the author, all the 

 facts point to the conclusion that from their earliest appearance the 

 germ-cells are to be regarded as specific elements. In conditions not 

 markedly divergent from the normal they do not change into somatic 

 cells, nor do they arise from them. 



* 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 pub- 

 lished, and to describe and illustrate Instruments, Apparatus, etc., 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, Reproduction, and 

 allied subjects. 



X Arch. Mikr. Anat., lxxxv. (1914) 2te Abt., pp. 9-113 (6 pis. and 7 figs.). 



