320 SUMMARY OF CURBENT RESEARCHES RELATING TO 



becomes foul or the temperature too low. It first bends on itself and 

 remains quiescent for several days. If the unfavourable conditions 

 continue, it surrounds itself loosely with mucus, which hardens in the 

 water. Turning slowly round and round, secreting threads of mucus as 

 it does so, it generally makes a cyst of concentric layers enormously 

 bigger than itself. Within this it may remain absolutely quiescent for 

 a month. The author also notes that Tetrastemma dorsale often encysts 

 along the outside of the tube of Tub id aria indivisa. The tubular cyst 

 thus formed has the same structure as that of Prostoma, but the retreat 

 is of short duration. 



Summer and Winter Spawning in a Fresh-water Nemertean.* 

 Paul Hallez observed Prostoma lumbrkoidmm Duges, spawning in an 

 aquarium in October, November, and February. It deposited on the 

 the glass 10 to 15 eggs united by a mucous substance. The eggs 

 developed quickly, hatching in 10 to 12 days. In December he also 

 observed spawn, but very different. The worms formed a protective 

 spherical cyst and filled them with eggs, about seventy in all. There was 

 nutritive material around the eggs, and the development was very slow. 



Ookinesis in Cerebratulus lacteus.j— Nashide Yatsu describes the 

 maturation and fertilisation of the eggs of this Nemertean. We quote 

 his general conclusions. The nuclear fluid is similar to hyaloplasm. 

 It is usually neither alveolar nor reticular, but homogeneous. Diminu- 

 tion of chromatin (basichromatin) does not take place at the dissolution 

 of the germinal vesicle. The centrosome is a temporary accumulation of 

 cytoplasm around the centriole, which is a centre for the formation of 

 rays. Its size is proportional to that of the cell. The spermatozoon 

 carries a centriole in its middle piece into the egg at fertilisation. This 

 gives rise to the cleavage centrioles, whose position is determined by the 

 egg-organisation. Rays may be formed in homogeneous as well as in 

 alveolar plasm. In fixed material fibrous and non-fibrous rays can be 

 distinguished. 



Incertes Sedis. 



Australian Fresh-water Polyzoa.J — E.'J. Goddard has taken up 

 the study of these forms, to which little attention has been paid for over 

 twenty years. He describes FredericeUa australiensis sp. n., and gives 

 a list of recorded species. 



Indian Ocean Pterobranchia. — A. Schepotieff describes two interest- 

 ing forms, Rltabdopleura striata sp. n., Cephalodiscus indicus sp. n. and its 

 larva. In the new Rhabdopleura the raised tubes are built of plates 

 arranged in regular circles ; the stolon is hollow so that the trunk-cavities 

 of the individuals are all in communication ; there is a close general 

 resemblance to R. normanii Allnian. In the new Cephalodiscus the 

 ecenceciuni has numerous separated cavities, each with a single aperture. 



* Comptes Rendus, cl. (1910) pp. 556-7. 



t Journ. MorphoL, xx. (1909) pp. 353-401 (4 pis.). 



J-Proc. Linn. Soc. N.S.W., xxxiv. (1909) pp. 487-96 (1 pi.). 



§ Zool. Jahrb., xxviii. (1909) pp. 429-48 (2 pis.). 





