Porifera. 



sheath (Spicula-Oberhaut) which seems to be different from what is generally 

 called ^)Spicula-Scheide by the German authors. Das Wachsthum der Skelett- 

 spicula durch Apposition ist nicht ausgeschlossen, es ist vielleicht sogar wahr- 

 scheinlich; die Hautspicula konnen sich auf dem Wege der Apposition nicht 

 wesentlich vergroBern. No epithelium is found in the outer surface. Silicoblasts 

 and spongoblasts lie in sheaths or membranes around the bundles of spicules. The 

 canal-system is eurypylous. Pores and oscula do not differ much in size and ap- 

 pearance. 



Regenerative capsulesw in Reniera, see Thomson, infra, p 9. 



Anatomical details of Reniera, Amorphina and Dendoryx, see Topsent ( 2 ) . 



Gemmules in vChalina oculata and gradients, see Topsent (*). 



Weltner kept Spongilla and Ephydatia alive after their production of larvae, by 

 which experiment it is proved that Laurent and Goette were wrong. Against 

 Marshall the same author found that there is no such thing as Saisonverschieden- 

 heit, nor Generationswechsel. 



Fiedler distinguishes in Spongilla Jluviatilis two classes of cells : those with a 

 regularly granulated and those with an irregularly granulated protoplasm. The 

 former, characterised by the facts that the granules are more easily and firmly 

 stained by aniline-dyes and that the nucleus shows a kind of network (Gerust) , 

 are situated especially immediately under the surface of the sponge. They are 

 large and amoeboid, and act as phagocytes (Fresszellen) . The flat epithelial 

 cells have nothing to do with nutrition, as v. Lendenfeld and others think. The 

 cells with an irregularly granulated protoplasm are much more frequent. There 

 are no muscles nor muscle-cells, because there are no nervous elements, either in 

 Sycandra, or in Spongilla. There are special wandering-cells, for the nutrition 

 of the ovum, with very unequal granules; these amoeboid cells are not to be con- 

 founded with the phagocytes, mentioned above. It is not true that the ova may 

 develop from every cell of the parenchyme. They may be derived from those 

 cells which possess an irregularly granulated protoplasm and a nucleus provided 

 with a nucleolus. A rather detailed description is given of these ova, which, in 

 summer, are to be found throughout the whole sponge ; there being therefore no 

 localisation. Against Goette and others, F. states that the small yolk granules are 

 the first and that these by growth become the large ones. In very young ova the 

 presence of minute yolk-particles is proved by staining with Bleu-de-Lyon. In 

 the beginning these particles originate from the ovum plasma, afterwards also 

 from certain cells (NahrzelIen) between the follicle-cells, which by a mixture of 

 chromic, osmic and acetic acids are stained exactly like the yolk particles of the 

 ovum. The existence of polar bodies has been already mentioned in the prelimi- 

 nary report [cf. Bericht f. 1887 Porif. p 8]. The entrance of spermatozoa into 

 the ova was never observed. The nucleus is of great moment in the segmentation ; 

 on this account double-staining is required. It is not due to the great quantity 

 of the deutoplasma that no nuclear figures are visible, at least not in the manner 

 that the author believed in his preliminary report. He considers that he has to do 

 with a transitional form between direct and indirect segmentation of the nucleus. 

 Nucleus and nucleolus form one sphere (kuglige Gebilde), and then begin to 

 divide. Besides this direct division in the ova, there is in Spongilla an indirect 

 division in certain cells, showing the well-known figures, as first observed by 

 Weltner. The development of the spermatozoa is not quite as was described in 

 the preliminary account. It was stated there that the type followed was the 

 Schulze-Typus. The author now finds it to be between that and the Polejaeff- 

 Typus, but resembling more the latter. 



Hintle gives a description of some new species of Uruguaya. 



