704 SUMMARY OF CUBRENT RESEARCHES RELATING TO 



SUMMARY 



OF CURRENT RESEARCHES RELATING TO 



ZOOLOGY AND BOTANY 



{principally Invertebrata and Gryptogamia), 



MICROSCOPY, &c., 



INCLUDING ORIGINAL COBIMUNICATIONS FROM FELLOWS AND OTHERS.' 



ZOOLOGY. 



A. GENERAL, including Embryology and Histology 

 of the Vertebrata. 



Embryology of the Sheep.f —Dr. E. Bonnet has investigated the 

 earlier stages of development in the sheep embryo. 



His positive results commence from the twelfth day after impreg- 

 nation. Embryos of this age showed round, uniformly bilamellar, 

 germinal vesicles, with a round, bilamellar, embryonic disk of about 

 •25 mm. in diameter. The epiblast of the disk consisted of two or 

 three layers of cylindrical cells continuous with the flattened ecto- 

 blast of the vesicle. The entoblast formed a single distinct layer of 

 cells, distinguishable into two classes, according to position, viz. : — 



1. Ovoid cells, beneath the disk. 



2. Flat cells, forming a retiform membrane, lining the vesicle 

 generally. 



The ovoid cells form "the entoblast of the (future) digestive 

 tract," the flat peripheral cells " the entoblast of the yolk-sac." 



On the thirteenth day there appears in the vesicle, peripherally 

 to the disk, a formation of mesoblast in the vesicle. No trace of such 

 a mesoblastic growth is found at this stage in the disk. 



Within the disk, mesoblast is formed a little later in a twofold 

 manner. Beneath what eventually is the primitive groove there is 

 formed an ectoblastic " thickening" {Knoten). From this is developed 

 the "central" or " ectoblastogenous " mesoblast, which remains in 

 direct and intimate connection with the ectoblast axially. The 

 "peripheral" or " entoblastogenous " mesoblast arises as a peripheral, 



* The Society are not to be considered responsible for the views of _ the 

 authors of the papers referred to, nor for tlie manner in which those views 

 may be expressed, the main object of this part of the Journal being to present a 

 summary of the papers as actually published, so as to provide the Fellows with 

 a guide to the additions made from time to time to the Library. Objections and 

 corrections should tlierefore, for the most part, be addressed to the authors. 

 (The Society are not intended to be denoted by the editorial " we.") 



t Arch. f. Anat. u. Physiol. (Anat. Abthcil.) 1884, pp. 170-230 (3 pis.). 



