ZOOLOGY AND BOTANY, MICEOSCOPY, ETC. 545 



Regeneration of Gunda ulvse.* — D. J. Lloyd has made a series of 

 experiments on the marine Turbellarian, Gunda ulvse, with the object 

 of discovering how far it could be made to undergo variation while 

 regenerating lost parts, and if possible, of correlating the variations with 

 definite physical conditions. It was found that G. ulvse is capable of 

 living indefinitely in water having an osmotic pressure of more than 

 2 and less than 33 atmospheres. The rate of regeneration of the 

 posterior end in G. ulvse depends on the osmotic pressure of the medium. 

 This osmotic pressure has an optimum value for regeneration at 18 atmo- 

 spheres, i.e. just below that of sea-water, and limiting values at 5 and 

 33 • 5 atmospheres. Restoration of lost parts in G. ulvse is brought about 

 entirely by the undifferentiated parenchyma cells which migrate to the 

 region of the wound and build up the lost parts. For values of the 

 osmotic pressure lying between the optimum and the limiting values, 

 this migration of the parenchyma cells is retarded, and the rate of 

 restoration is retarded to a similar degree. At the limiting values 

 of the osmotic pressure there is no migration of the parenchyma cells, 

 and no restoration of lost parts. Under starvation conditions G. 

 ulvse undergoes reduction. This consists in absorption of the genital 

 system and in reduction in size. Both these are brought about by the 

 activity of the parenchyma cells. During the process of restoration of 

 lost parts the same reduction processes occur as in starvation. Where 

 the restoration of lost parts is retarded, e.g. by raising or lowering the 

 osmotic pressure, reduction is retarded to precisely the same extent. In 

 sea-water or hypertonic solutions removal of the posterior half of the 

 body inhibits further production of sperm. In hypotonic solutions 

 sperms continue to be produced for a varying length of time. In 

 strongly hypertonic solutions examination of the gut cells shows that 

 these have diminished and become more dense. In strongly hypotonic 

 solutions they have increased in size and become vacuolar. 



Thalassema and a New Related Genus.f — L. D. Wharton describes 

 Thalassema sorbillans Lampert, T. semoni Fischer, T. formulosum 

 Lampert, and T. griffini sp. n., all from the Philippines. A full 

 account is given of the body-wall of the new species. It consists of 

 cuticle, epidermis, dermis— the muscular layer, and an endothelium. It 

 is divided into eighteen longitudinal intermuscular spaces, or "intervals," 

 by eighteen longitudinal muscle bundles ; and these intervals are again 

 divided transversely into rows of narrow compartments, or " stomata," 

 by septal bands and oblique bundles. An unusually clear diagram is 

 given, of a type which should be imitated. Each of the stomata is 

 connected with the ccelom and filled with coelomic fluid. The contrac- 

 tion of the muscles accounts for the small square elevations on the skin 

 of the living animal. As the stomata are covered only by the corium 

 and a very thin layer of circular muscle, it seems reasonable to suppose 

 that the stomata are connected with respiration. The details of the 

 dermal muscle layer are useful in classification. A careful account is 



* Proc. Roy. Soc, lxxxviii. (1914) pp. 1-27 (16 figs.). 



t Philippine Journ. Sci., viii. (1913) pp. 243-70 (2 pis. and 3 figs.). 



Dec. 16th, 1914, 2 o 



