420 RECOED OF CURRENT RESEARCHES RELATING TO 



vera (on the side of the sinus) and a reflexa on the respiratory 

 chamber wall. The latter consists of two ejiithelial layers enclosing 

 connective tissue, and is perforated by an aperture closed by epithe- 

 lium ; this is the mouth of the uterus, and afterwards gives passage to 

 the embryo. By the contraction at this time of the blood-sinus walls 

 round the follicle, the walls of this, which become cavernous, form a 

 maternal placenta.- A chorion is formed by the fusion of the decidua 

 which lies on this side of the ovum with the ovisac. 



The blastocoele (segmentation cavity) appears on the same side of 

 the ovum ; and here the blastoderm consists of the morula cells com- 

 bined with those of the ovisac and the decidua ; on the opposite 

 hemispheres the segmentation cells subsequently form the epiblast ; 

 a small group of them in its centre forms the rudiment of the cerebral 

 ganglion ; close to this some surviving small cells become invaginated, 

 and an amnion which adheres to the ganglion is the result. 



The hypoblast originates in some cells derived from the lecithin 

 cells, occurring between the blastocoele and the epiblast ; it is folded 

 over towards the blastocoele and encloses a cavity, the primitive intes- 

 tine. Of two layers which are differentiated from the epiblast, the 

 inner one develops a fold which jjrojects inwards and joins the 

 hypoblast opposite to the point of closure of the primitive intestine ; 

 a canal appears in it and leads ultimately into the intestine ; the epi- 

 blast also forms the ectoderm and secretes the cellulosa externally. 

 The cells within the ganglion rudiment form a transitory, elongated, 

 longitudinally grooved thickening, — the dorsal plate. The hypoblast 

 consists first of two strata : the internal becomes the endoderm : the 

 external one, forming the mesoderm, gives rise to the muscular ele- 

 ments ; the blood and connective tissue arise from cells derived from 

 the internal side of the blastoderm. From the cells within the invagi- 

 nation-mouth arises a transitory organ, the " dorsal disk." 



The cells of the outer side of the blastoderm form the foetal 

 placenta. The equatorial segmentation cells form the so-called " ger- 

 minative ring," giving rise to a membrane from which the cells which 

 later originate the stolon are derived. 



It is the varying extent to which the nutritive is combined with 

 the formative yolk, which appears to produce such varied transforma- 

 tions in this ovum. 



Arthropoda. 



o. Insecta. 

 Testes of the Lepidoptera.* — Herr Cholodkowsky here adds to 

 and formulates the present state of knowledge as to the anatomy of 

 these organs. He finds that the testis, even when outwardly single, 

 is always primordially made up of several tubes. This was already 

 known to be the case in Hepialus humuU, where the two tubes each 

 branch into four, also in larvae, and in the embryos of many species. 

 His investigations, made on 34 species of Ehopalocera, taken from 

 17 genera, demonstrate the primordial division of the testis into eight 

 tubes in all. The tubes are shown by steeping the male organs in 75 per 



* 'Zool. Anzeiger,' iii. (1880) p. 115. 



