704 SUMMAKY OF CUKKENT KESKAK01IES RELATING TO 



SUMMABY 



OF CURRENT RESEARCHES RELATING TO 



ZOOLOGY AND B T A N V 



(•principally Invertebrata and Gryptogamia), 



MICROSCOPY, &c, 



INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS.* 



ZOOLOGY. 



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



a. Embryolog-y.f 



Oogenetic Studies.^ — Dr. L. Will, in the first of Lis oogenetic 

 studies, deals with the history of the ovum of Colymbetes fascus. 



Treating first of the primordial ovum and its conversion into a 

 multicellular ovarian mass, he describes the former as similar to that 

 of other animals and especially of Vertebrates ; in its development, 

 however, it exhibits some interesting and characteristic peculiarities. 

 The nucleus of the primordial ovum gives rise to large daughter-nuclei, 

 and these become the nuclei of those elements which are ordinarily 

 called yolk- or nutrient-cells, but to which Dr. Will applies the term 

 of giant epithelial cells, as they have absolutely nothing to do with 

 nourishment or with yolk-formation. They pass to the perijmery of 

 the egg, but not in such a way as to form a closed follicle round it ; 

 they rather occupy one side of the egg ; the large ovarian nucleus 

 is thus pressed towards the opposite side of the cell, and a longi- 

 tudinal axis becomes apparent later on. Smaller daughter-nuclei arc 

 also formed, and these become the nuclei of the true epithelial cells 

 or those which will, later, surround the egg with a continuous follicle. 

 At first the primordial ovum is undoubtedly a single cell, but on the 

 formation of daughter-nuclei it loses its unicellular character, and at 

 the time when all the large daughter-nuclei are formed the primitively 

 unicellular primordial ovum becomes a multicellular ovarian rudiment; 

 the true ovum is formed solely by a single cell of this mass, and by 

 the one which contained the primitive ovarian nucleus, and which 



* 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 (if 

 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 processes of Evolution, Development, and 

 Reproduction, and with allied subjects. 



j Zeitschr. f. Wise. Zool., xliii. (1886) pp. 329-G8 (2 pis.). 



