50 SUMMARY OF CURRENT RESEARCHES RELATING TO 



an interesting parallelism in development to ova, Ova in sponges arise 

 normally from clusters of archaeocytes, but of these certain lose their 

 individuality, and are sacrificed to feed the one successful ovum-cell. 

 The buds of Tethya arise from similar groups of archaeocytes, but here 

 the cells for the most part retain their individuality, though even here 

 certain of them fuse together to form a few large complexes similar to 

 blastomeres, within a chitinoid capsule. A further even more striking 

 resemblance between developing bud and developing egg is that, before 

 the sponge-bud becomes functional, its cells become arranged in two 

 layers, an inner gastral, and an outer dermal, and the development of 

 the central cavity and flagellated chambers takes place according to 

 methods comparable to those exhibited by other groups of sponges. 

 The method of formation of the chambers, whether lacunar or parenchy- 

 matous, depends in sponges in general on the time at which histological 

 differentiation takes place. In Calcareous Sponges this differentiation 

 occurs first during or after fixation ; in Siliceous Sponges often in the 

 larvae or even in the embryo. In Tethya the method of development 

 approaches the one condition or the other, according as the bud is 

 liberated early or late. A striking difference between the development 

 of the buds of Tethya, and of the embryos of other sponges, lies in the 

 fact that in the latter case the flagellated cells, which are not here tem- 

 porarily required for locomotor purposes as in the larvae of other forms, 

 develop late instead of early, and the remarkable metamorphosis of 

 larval development is therefore here absent. But this mode of develop- 

 ment by buds must be looked upon as secondary and not primary, as 

 derived from a sexual condition. 



Suberites domuncula.* — J. Cotte discusses the commensalism be- 

 tween this interesting sponge and the hermit-crab, but, in particular, 

 the chemical composition of the body. It is very rich in bromine, with 

 traces of iodine ; without iron or arsenic ; with some manganese along 

 with the silicon in the ash. He found no mucin, uric acid, fat, or 

 glycogen, and very little starch. The pigment is regarded, with 

 Krukenberg, as a kind of tetronerythrin ; it is not due to symbiotic 

 Algae ; it is usually orange-yellow, but may be blue on the surface. 



A study of the expressed juice showed the presence of many kinds 

 of ferments : — oxydising (?), diastatic, fat-splitting, proteolytic, &c. 



Protozoa. 



British Fresh-water Rhizopods. f — Prof. G. S. West contributes 

 notes on G8 species of Rhizopods (including Heliozoa) which he has 

 observed in Britain. He describes as new species Cochliopodium longi- 

 spinum, C. minuium, Gromia stagnalis, Acanthoeystis paludosa, &c. ; and 

 establishes a new genus Leptochlamys, undoubtedly near to Penard's 

 Crypt odifflugia. Some of the observations in the paper relate to the 

 habits and structure of well-known forms ; others are descriptive of 

 peculiar variants in common species ; others again are records of rarer 

 and less-known species. A point of considerable interest is the presence 



* Notes Biologiques sur le Suberites domuncula, Paris, 1901, 128 pp. See ZooL 

 CentraJbl., viii. (1901) p. 501. 



T Journ. Linn. Soc. Zool., xxviii. (1901) pp. 308-42 (3 pis.). 



