B. Porifera incalcaria. 5 



[Vioa Grantii Schmidt = Cliona vastißca). Genus (2) Thoosa Hancock, always 

 possessing small nodulons amphiasters , generally other amphiasters, reduced 

 oxyasters, and sterrasters, sometimes megascleres. Genus (3) Alectona Carter, 

 containing amphiasters of various form, reduced oxyasters, and oxeas covered with 

 tubercles. The genus Samus consists of boring Tetractinellid sponges, it does 

 not enter into the group of the Clionidae. 



Jennings observed some trifling variatious in Alectona millari. 



2. Cornacuspongiae. 



A. Halichondrina. 

 See Hanitsch, Keller (^j, Topsent (3), Topseiitl^) (2 n. sp.), Weltner. 



Dendy (^) gives a short account of the anatomy of Halichondria panicea. The 

 canal System is lacunar, the flagellated Chambers are »sub-spherical«. Sollas's 

 membrane is distinctly visible, and flagella were observed coexisting with it. Ova 

 were seen, hanging in a thickish envelope in the lacunae. — Grentzenberg states 

 on the contrary: »das Canalsystem von Hai. panicea würde dem vierten Typus 

 zuzurechnen sein«. 



Wilson found gemmulae in Esperella fibrexilis n. Certain cells of the paren- 

 chyme »are much larger than the rest and have plump bodies, which staiu well. 

 Such cells congregate together and form irregulär gronps in which the cells are 

 rather closely packed«. The outer cells become flattened and form a follicle. 

 » The increase in size of the gemmule takes place by means of cell growth and 

 division, and by the fusion of neighbouring small gemmules«. During the growth 

 of the gemmule »the surrounding tissue becomes largely incorporated in the 

 follicle«. In its ripe condition it lies in one of the larger canals^ suspended by 

 Strands of tissue. The gemmule then splits up into irregulär masses of cells, 

 which soon arrange themselves so as to form a peripheral layer and a mass of 

 amoeboid cells within it. The outer cells become columnar and get cilia, except 

 at one pole, where they remain flat and without cilia. Meantime spicules are 

 developed at the non-ciliated pole, and the larva breaks through its follicular 

 wall. Soon the whole epithelium is flattened and the larva is fixed at the spicular 

 pole. After fixation subdermal cavities and canals appear. The flagellated Cham- 

 bers arise as independent structures, which subsequently acquire connection with 

 the canal System. They originate from solid cell-groups. — This mode of de- 

 velopment agrees exactly with what we know of many larvae originated from 

 fertilised ova; the author, however, believes that these larvae oi Esperella fihre- 

 xilis are »asexual larvae«, i. e. originated from simple gemmulae. 



Delage gives an account of the homology and fate of the flagellate cells (cellules 

 ciliees) coveriug the larva oi Spongilla [cf. Bericht f. 1890 Porif. p 3]. His de- 

 scription contradicts especially the observations of Maas [cf. ibid. p 5] and generally 

 the views of all other zoologists. The adult ectoderm arises from a discontiuuous 

 layer of large rounded cells , which , in the free larva , lie under the » cellules 

 ciliees (f. On fixation the two series of cells change places, the »cellules ciliees« 

 lose their flagella and in their turn form a layer of rounded cells immediately un- 

 der the now nascent ectoderm. They are not allowed to rest here, but the great 

 cells of the central mass come into piay ; each, protrudingnumerousandactivepseu- 

 dopodia, catches and devours as many of the »cellules ci-devant ciliees« as it can 

 reach. A few are digested, the majority »apres un repos de 24 ä 36 heures« succeed 

 in making their escape; they now enter on their true function in life, the formation 

 of the lining to the canals and the flagellate Chambers. Their amoeboid captors 

 become mesodermal cells of the adult. The development in Äplysilla is similar. 



Zool, Jahresbericht. 1891. Porifera. f. 



