56 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Egg fragments from which a large portion of the micromere pole has 

 been removed before the fourth cleavage, are capable of producing 

 micromeres. Pieces, consisting of two nucleated portions of the 4-cell 

 stage produced by a vertical cut, exliil)it half-cleavage. In operated 

 eggs both the middle and the end-cells may each divide equally into 

 two, instead of giving off micromeres. 



Porifera. 



Association of Suberites and Dromia.* — 0. Polimanti has studied 

 the partnership between Suberites domuncula and Dromia vulgaris. He 

 discusses, in particular, the origin of the association. It is certain that 

 the crab takes the initiative in putting the sponge on its cephalothorax. 

 It is also certain that the sponge affords the crab a genuine protection 

 against the appetite of cuttlefishes. 



Regeneration in Sycon.f — Julian S. Huxley confirms H. V. Wilson's 

 observations on the coalescence of cells strained off from chopped-up 

 sponge. He worked with Sijcon rhaphanus. The cells united, mainly 

 by means of actively amoeboid cells, into small lumps of irregular shape, 

 in which the various kinds of cells were confusedly mixed. This ended 

 the process of reunion —one that does not normally occur in nature. 



There followed a process of reorganization, similar in its main features 

 to what occurs during reversal of the layers in the parenchymula larvae 

 of Calcarea ; the dermal cells migrated to the surface to form a flat 

 -epithelium round a solid central mass of quiescent collar-cells. The two 

 layers of the sponge-body are now present in their definitive positions, 

 and the subsequent period may be called one of re-development. 



What occurs is practically the same as in the normal post-larval 

 development. Spicules are formed, first monaxons, then triradiates ; a 

 gastral cavity, and finally an osculum appears. None of the regenerates 

 reached a heterocoele condition, but one lived and grew as a functioning 

 sponge for several weeks. 



By other methods collar-cells were obtained nearly or quite pure. In 

 various ways these formed spheres. Though some lived for over a 

 month, no other form of tissue was ever regenerated. This is not 

 necessarily either for or against the theory of a choanoflagellate ancestry. 

 The formation of volvox-like spheres may be due to the oxygen require- 

 ments and to surface tension. The failure to regenerate other tissue 

 may mean that the more ancestral cells have given up their regenerative 

 power to others more suited to the work. 



Examination of the collars has shown that, in S. raphanus at least, 

 the longitudinal supporting rods described by Bidder exist during life as 

 well as in preparations. 



Division of Collar-cells of Calcarea Heteroccela.J — Muriel Robertson 

 describes this in (Jrantia compressa and a species of Sijcon, with par- 

 ticular reference to the behaviour of the basal granule or blepharoplast of 

 the flagellum. In the vegetative condition of the cell the blepharoplast 



* Zool. Jahrb., xxx. (1911) pp. 359-76 (3 figs.). 



t Phil. Tranp., B, ccii , pp. 165-89 (1 pi. aud 5 figs.). 



X Quart. Journ. Micr. Sci., Ivii. (1911) pp. 129-39 (1 pl.V 



