ZOOLOGY AND BOTANV, MICROSCOPY, ETC. 51 



and the early stages of oogenesis is emphasised. The question of the 

 factors determining gemmation or sexual reproduction is discussed. 

 There is a correspondence between a constitutional " depression " of the 

 polyp and the development of gonads. 



Porifera. 



New Desmacidonidse.* — W. Lundbeck reports on some of the 

 Desmacidonidfe (the Esperellinte, seu Mycalinaj) of the ' Ingolf ' Expedi- 

 tion, discussing 14 genera and 69 species, of which o2 are new. 

 Considerable attention is paid to the characterisation of the chele and 

 anchor spicules. 



Development of Sycandra raphanus.f — -E. Hammar found sexually 

 mature individuals at every season of the year at Naples. The ova arise 

 from amoeboid wandering cells in the middle stratum, and devour other 

 amceboid cells. After the larvae fix themselves, an indefinite middle 

 stratum appears. It did not seem as if the spicules had an intra-cellular 

 origin. The flat epithelium lining the oscular-tube and the proximal 

 parts of the radial chambers seemed to be endodermic in origin, as if 

 modified from the flagellate cells of the larva. The latter seem to have 

 no collar. Like the collar-cells of the adult, they have a distinct 

 blepharoplast from which the flagellum springs. In well-preserved 

 material Hammar could not find Sollas's membranes, rod-like structures 

 in the collar, or iris-like basal diaphragms. 



New Siliceous Sponges from Africa. J — L. Baer reports on four 

 species of Tetraxonida, and sixteen species of Monaxonida (of which 

 fifteen are new), from Zanzibar, Cape Town, and Papeete. 



Sponge Spicules. § — Celso Arevalo has made some optical investiga- 

 tions on the siliceous and calcareous spicules of Spanish sponges, e.g. of 

 Leuconia, and propounds a theory of their mode of formation. 



Protozoa. 



Chemical Nature of Acantharian Skeleton.|l— 0. Biitschh finds 

 that the skeletal substance of Podactuielius and other Acautharia consists 

 mainly of strontium sulphate, probably in the form of coelestin or the 

 like. 



Studies on Acanthometridse.lF — W. Mielck communicates some of 

 the results of his studies on Pacific Ocean Acanthomethridse, especially 

 as regards the skeleton — the number and arrangement of the spines, the 

 central union of the radial spines, the cross-sections of the spines, and 

 so on. The genus Acanthonia seems to represent the phyletically oldest 

 group of Acanthometridae with radial spines. 



» Danish ' lugolf ' Exp., vi. part 2 (1905) pp. 1-219 (20 pis. aud 7 figs.), 

 t SB. Ges. Natur. Berlin, No. 5 (1906) 4 pp. See also Zool. Zeutralbl., xiii, 

 (1906) pp. 451-2. 



j Arch. Natur., Ixxii. (1906) pp. 1-36 (5 pis.). 



§ Boll. Soc. Espafi. Hist. Nat., vi. (1906) pp. 368-75 (3 figs.). 



II Zool. Anzeig., xxx. (1906) pp. 784-9. 



t Tom. cit., pp. 754-63 (3 figs.). 



E 2 



