766 SUMMARY OF CURRENT RESEARCHES RELATING TO 



the end of this tube which was directed centrifugally in rotation. When 

 regeneration took place, the red pigment which marks the fnt are hydranth 

 pole could be seen collecting in the compressed protoplasm, and it 

 gradually migrated np the tnbe of perisarc until it reached the end of 

 this tube, whereupon the tentacles and other parts of the normal 

 hydranth appeared. The generalization may be made that polarity in 

 Tubularia erocea cannot be altered by the action of centrifugal force, in 

 shifting "organ-forming areas" from one end of the piece of stem to 

 the other. 



Porifera. 



Development of Sponges from Dissociated Cells.* — H. V. Wilson 

 squeezed out cells, e.g. of Microciona prolifera, and put a drop of the 

 " sediment " on a slide. The cells fuse into syncytial masses or plasmodia, 

 these may fuse into incrustations, and these may form sponges. The 

 details of the interesting process are described. Experiments were also 

 made with Lissodendoryx carolinensis sp. n. and Stylotella heliophila sp. n. 

 in both of which the dissociated cells formed plasmodia. When dis- 

 sociated cells of Microciona and Lissodendoryx are mingled, they do 

 not fuse. The same is true of Microciona and Stylotella ; the cells of 

 one species fuse, the plasmodial masses of one species fuse, but there is 

 no fusion between the tissues of two separate species. The author thinks 

 that when the cells are violently dissociated in his very interesting ex- 

 periments they pass into an indifferent generalized state. In this state 

 they re-combine to form a mass of undifferentiated tissue comparable to 

 a heap of blastomeres, in which differentiation and growth occur. 



Classification of Halichondrina.f — E. Topsent has studied the 

 larvae in this sub-order of sponges, and re-adjusts the classification a little 

 in the light of his observations. There are four families. 1. The Hali- 

 ehondridfe have larvae completely ciliated and of uniform colour : — 

 Halichondria, Tedanione, Ephydatia, etc. 2. The Haplosclerida? have 

 the larvae naked posteriorly, with a crown of long cilia and a ring or cap 

 of pigment : — Reniera, Chalina, C/ial inula, Gellius, Desmacidon, etc. 

 3. The Poeciloscleridaj have the larvae naked posteriorly, without a crown 

 of long cilia, and with the posterior hernia paler than the rest : — Mycale, 

 Tedania, Myxilla, BatzeUa, Clathria, Echinodictyum, etc. 4. The Axi- 

 nellidae, with larval characters a little like those of the preceding family, 

 but with different spiculation. 



Sponges associated with Vermetida34 — X. Annandale describes 

 rocky masses dredged from the Bay of Bengal which consist of the shells 

 of /Sil/quaria muricata (Born.), S. cochlear is Morch, and Spiroglyphus 

 cvmmingi (.Morch), closely associated with sponges, namely two new 

 varieties of the Lithistid Racodiscula sceptrellifera (Carter), and the 

 Monaxonid Spongosorites topsenti Dendy. Neither of the two species of 

 sponges found associated with the three species of Vermetidae is peculiar 

 to these shells, nor, indeed, to a habitat or manner of life similar to that 



* Bull. Bureau Fisheries, xxx. (1910, published 1911) pp. 1-30 (5 pis.), 

 t Arch. Zool. Exper., viii. (1911) Notes et Bevue, No. 1 pp. i.-xv. (4 figs.). 

 X Becords Indian Museum, vii. (1911) pp. 47-55 (2 pis.). 



