Porifera. 



but the author could only see a further (?) .stage in which each chela was sur- 

 rounded by 4 nuclei. At the proximal area, the nuclei of the most peripheral 

 cells lie just at the border. In normal cases the development goes very rapidly. 

 Within 6-24 hours they are fixed and the metamorphosis has begun. The pro- 

 ximal area is normally fixed (75 cases, against 15 in which the larva was fixed at 

 the distal end). Sections of fixed larvae showed in the beginning of the metamor- 

 phosis that they were flattened and that the greater mass of the little cells which 

 were formerly at the periphery, now lie more central. The sponge is covered by 

 an epithelium like that of the naked part of the free larva. The author never 

 saw that the flagellated cyliudric epithelium changed into this sort of epithelium 

 and can hardly believe this to be possible. - - The subdermal cavities are the first 

 lacunae to appear in this stage, soon accompanied by flagellated chambers and 

 canals. The chambers probably originate from complexes of the little cells which 

 in the larva lie more peripheral. These cells also give rise to exhalant canals and 

 lacunae. According to Maas (', 2 ) the larva of Esp eria [Esperella} consists chiefly 

 of two different layers (Lagern) : a layer of small elongated flagellated cells with 

 small nuclei at the proximal portion of the larva: and secondly a thick layer of 

 larger cells some of which bear spicules, occurring at the distal end and the greater 

 part of the inner mass of the larva. The larva is fixed with the proximal area, 

 and then the small cells with small nuclei are situated in the center, and the rest 

 of the cells grow round them. The small cells give rise to the flagellated chambers 

 and the exhalant canals; the larger cells do the rest. Therefore the author accepts 

 only two wKeimblatter in E. and compares these to the two primitive germinal 

 layers of Sycandra etc . 



Delage describes the postlarval development of Esperella sordida. The sur- 

 face of the free larva is ciliated with exception of the posterior part. There is no 

 cavity ; the same kinds of cells occur as in Spongilla [see infra]. The epidermie 

 cells lie partly between the flagellated cells, partly in several layers nearer the 

 center. Spicules are only present in the posterior area. Fixation takes place 

 at varying parts except at the naked posterior end. The flagellated cells lose 

 their flagella and move inwards as in Spongilla. Part of them are devoured by 

 amoeboid cells, part of them form groups, which become hollow and thus give 

 origin to flagellated chambers. The latter grow larger by admission de cellules 

 nouvelles et multiplication de leur cellules primitives^. - The post-larval deve- 

 lopment of vReniera densa in most respects is very like that of Esperella. The 

 larva possesses a ring of very large flagella at the limit of the flagellated and the 

 naked portion of the larva. 



Topsent ( l ) describes Potamolepis barroisi n. sp. from Tiberiade Lake, Syria. 

 It possesses oxea only. 



Buck cultivated Ephydatia mi'dleri in small tanks ; a piece was torn off, which 

 grew out to a new sponge. The spermatozoids of this piece probably fertilized 

 the ova of the original stock. After 5 months 4 young sponges were visible, fixed 

 at some distance from the mother-sponge. 



Delage describes the post-larval development of Sponyilla fluviatilis . The 

 free larva is partly hollow ; this place (anterior part) is empty ( vide ) or filled 

 with fluid. Four kinds of cells are to be distinguished: ^cellules ciliees ou fla- 

 gelle'es, cellules e'pidermiques , cellules amoeboi'des et cellules interme'diairescc. 

 The first in the larva serve for locomotion ; in the adult they become choanocytes. 

 The second in the larva lie under the flagellated cells in a discontinued layer; in 

 the adult they form the epiderme. The greater mass of larval cells are of the 

 third kind. In these cells spicules develope. The last kind in many respects stand 

 between the second and third; hence the name. After fixation the larva is 



