7l-0 SUMMARY OF CURRENT RESEARCHES RELATING TO 



Cell-division in Cerebraiulus.* — N. Yatsu has made experimental 

 studies (in the egg of Cerdbratulus, which seem to him to throw some 



light on the mechanism of cell-division. He finds that an enucleated 

 fragment with the aster shows a disturbance of surface tension, at the 

 end furthest from the aster. An enucleated fragment without the aster 

 often shows a division activity, and in some cases it is completely divided 

 into two. A mass of cytoplasm has in itself, or acquires under certain 

 conditions, the power of dividing itself, without the aid of either rays or 

 centrosomes. Cleavage goes on normally even after one of the centres 

 is cut off at an anaphase. After the cleavage is fixed, i.e. after the 

 formation of the diasteme, the cleavage furrows proceed normally, 

 notwithstanding the removal of a portion of the cytoplasm. Cleavage 

 between two asters with a spindle takes place perpendicularly to the middle 

 point of the spindle, irrespective of the position of the asters. One-sided 

 constriction of the first division may occur as in some Ccelenterates 

 and Petromyzon. The karyomeres may fuse and form a daughter- 

 nucleus, even when the chromosomes have been separated from the aster. 

 The same observer! publishes a note on the adaptive significance of the 

 sperm-head in the same form, Cerebratulus lacteus. From the fact that 

 it took the spermatozoa " considerable time and not a little effort " to 

 bore through the thick membrane in order to reach the egg, he con- 

 cluded that the long, slender, slightly-curved head of the spermatozoon 

 of C. lacteus might have evolved in corrtdation with the thick egg- 

 membrane characteristic of the species. A study of the relation of sperm- 

 head and egg-membrane in another species bore out this conclusion. 



Incertse Sedis. 



New Species of Dolichoglossus.J — Richard Assheton describes L. 

 serpent in us sp. n. from the littoral zone off Mull. Its total length was 

 200 mm. and upwards ; the contracted proboscis was 25-85 mm. long. 

 The proboscis is cylindrical rather than conical, and capable of great 

 extension. It is bright rosy red, the collar a deeper and more orange red, 

 the trunk from orange to yellow. There are about fiO pairs of respiratory 

 clefts in a large specimen ; there is no backward prolongation of the 

 collar over the gill-clefts. 



The animal has a strong " iodoform " scent. It is found in fine sand 

 at low-water mark, and is only very rarely uncovered by the tide. It 

 secretes much mucus, which forms tubes with the sand. Specimens were 

 kept alive for six months ; they never came entirely out of the sand, and 

 the collar was only once seen protruding ; the proboscis was frequently 

 protruded, especially at night, sometimes waving and curling in the 

 water, more usually lying along the surface of the sand, first in one 

 direction then in another. The only other Dolichofflossus recorded from 

 Great Britain is D. ruber, found by Tattersall on the West of Ireland. 



Colour Markings in a Devonian Brachiopod.§ — I). K. Greger 

 describes Grarmna morsii sp. n., which retains the original colour- 

 markings, sometimes in a very perfect condition. 



• Ann. Zool. Japon, vi., part 4, 1908, pp. 267- 7G. 

 t Biol. Bull., xiii. (1907) pp. 300-1 (2 figs.). 

 % Zdbl. Anzeig., xxxiii. (1908) pp. 517-20 (2 figs.). 

 § Amer. Joum. Sci., xxv. (1908) pp. 313-14 (7 figs.). 



