INVERTEBRATA, CRYPTOQAMIA, MICROSCOPY, ETC. 101 



amphiaster (RicLtungs-amphiaster) appears, marking the commence- 

 meut of the formation of the first pohir cell. As the latter is 

 segmented off, the female pronucleus (Eikeru) appears close beneath it. 



2. Comi)aralive Observations on the Egg.- — The early development 

 of the egg may take place in the following different ways : — 



(a) The changes in the germinal vesicle, up to the formation of 

 the amphiaster or the first polar cell, take place in the centre of the 

 egg (Hirudinea, Mollusca). 



(h) The division and subsequent disappearance of the germinal 

 spot takes place in the centre of the egg, but the germinal vesicle 

 passes to the periphery before forming the amphiaster (HydroiJs, 

 BatracMa). 



(c) The processes of division and solution of the germinal spot 

 are slow, and take place at the periphery of the egg (Asterids). 



(d) These processes again take place at the periphery, but arc 

 rapid (Echinids, Medusce, Siphonophora, Annelides, Lucernaridce ?, Mam- 

 malia ?). 



(e) The germinal spot does not divide, but undergoes solution as 

 a whole (Ascidians ?). 



Like other recent observers, Bergh considers that there is no 

 evidence in favour of Haeckel's theory that the egg-cell passes into 

 the cytode stage, by the total disappearance of the germinal vesicle. 



The latter part of the paper is taken up with a detailed account of 

 the process of yolk-division in Gonothynca, which closely resembles 

 that described in Hydra by Kleinenberg. 



The author concludes with some remarks upon segmentation and 

 cell-division in general. 



Porifera. 



Structure of the Spongidse.* — In the seventh instalment of his 

 •' Researches on the Structure and Development of Sponges," Piofcssor 

 F. E. Schulzo gives an account of the family Spongidno, whicli he 

 defines as " those horny sponges which have small, luains^jhcrical, 

 ciliated chambers, provided with special eflerent canals, and sur- 

 rounded by connective tissue rich in granules: a skeleton consist- 

 ing of a network of solid, concentrically laminated spongiolin fibres, 

 enclosing here and there foreign bodies, but never true siliceous 

 structures, and in which the filamentous knobbed filaments character- 

 istic of some families (Uirrlnidiv) are absent." 



The first section of the paper consists of a review of the work of 

 former observers on the classification, &c., of S])ongida) and on the 

 genera included in it. Of these Schulze accepts six : — Euspongia, 

 Hippoftpongia, PhyJIoapongia, Cartcriospongia, Cacospongia, and Sido- 

 spongia. 



Euspongia officinalis. — Schulzo distinguishes six subspecies of this 

 sponge, of the general character of all of which lie gives a descrip- 

 tion ; they are E. moUssimc, lamella, adriatica, irregularis, exigua, and 

 tidiidosa. 



As in other sponges, tlireo layers of tissue are distiuguisbuble, called 



* 'Zrit.sfli. wiss. Zoul.,' xxxii. (IsT'-O p. ;V.Ki. 



