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 SUMMARY 



OF CURRENT RESEARCHES RELATING TO 



ZOOLOGY AND BOTANY 



(principally Invertebrata and Cryptogamia), 



MICROSCOPY, &c, 



INCLUDING ORIGINAL COMMUNICATIONS FROM FELLOWS AND OTHERS.' 



ZOOLOGY. 



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



a. Embryology, t 



Animal Ovum.} — Prof. F. Leydig gives a preliminary notice of 

 the results of his investigations into the egg-cell. 



Germinal Rudiment and Egg-follicle. — It is now generally recognized 

 that the egg is from the first a cell, and that it does not commence as a 

 nucleus ; the error of observation is due largely to the small quantity 

 of protoplasm which often surrounds the nucleus. As bearing on the 

 question of the affinities of Annelids, Arthropods, and Vertebrates, the 

 author points out that if we can imagine a germ-cord from the stroma of 

 the ovary of a mammal it would have a close resemblance to free cords, 

 such as those of the leech. The earliest mark of differentiation is that 

 the cell-mass divides into germ-cells and matrix-cells, the former 

 becoming the primordial ova, and the latter the follicular cells ; these 

 latter excrete cuticular layers, so that the follicular wall becomes 

 thicker and takes on the character of connective tissue. The relation of 

 the secreting matrix-cells and the cuticle to the primordial ova is exactly 

 the same as that which obtains between the ganglionic sphere of a spinal 

 ganglion and the investment. A membrana granulosa, or layer between 

 the egg and the follicular wall is, when present, a later addition ; the 

 author is inclined to refer its origin to leucocytes and matrix-cells. In 

 Liihobius and Geophilus leucocytes certainly enter from the stalk of the 

 follicle, while in mammals the elements of the granulosa are derived 

 from the matrix and connective- substance cells of the follicle. The 

 granulosa of a mammal and the follicular epithelium of an insect appear 

 to be corresponding structures. 



Egg- cell. — Germinal spots are of two kinds ; some have the characters 

 of Amoebae with pale margins, and consist of spongioplasm, hyalo- 



* 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. 



% Zool. Anzeig., x. (1887) pp. (J08-12, G24-7. 



