304 SUMMARY OF CURRENT RESEARCHES RELATING TO 



The following hypothesis of cytoplasmic division is put forward. 

 The change of form is the result of two chief factors : (1) a definitely 

 localized increase of surface-tension, resulting directly from the increased 

 permeability and decreased electrical polarization of the cell-surface, 

 over two symmetrical areas centring at the poles and extending to near 

 the equator ; and (2) a secondary or adjuvant effect of the same kind 

 due to the diffusion of electrolytes (e.g. acid derived from oxidations) 

 from the astral centres or centrioles, which become chemically active at 

 this time. These centres appear to represent aggregations of a special 

 colloidal material which undergoes oxidation when the cell-surface 

 undergoes depolarization. 



Ccelentera. 



Luminescence of Cavernularia.* — E. Newton Parker has experi- 

 mented with the common Japanese Penuatulid, Cavernularia haberi, 

 which, if stimulated by touch, or electrically, or by the addition of 

 ammonia, gives off from its whole surface a brilliantly luminous slime. 

 The slime is produced by gland-cells, and contains minute luminous 

 granules. A considerable amount of oxygen is used up in light- 

 production, and there is no light v,ithout oxygen. The production of 

 light by the granules is comparable to the cytolysis of cells, as it occurs 

 with water (but not isotonic cane-sugar) and certain cytolytic substances 

 (saponin, chloroform, benzol, and oleic acid). 



Nervous Transmission in Actinians.f — G. H. Parker has experi- 

 mented with Metridium, and finds that nervous transmission may be 

 accomplished from almost any part of the ectoderm to its longitudinal 

 mesenteric muscles. Experiments in which the receptive part of the 

 anemone is connected with the effector portion l)y only a small bridge 

 of tissue, demonstrate that these nervous connexions occur in such a 

 variety of positions as to call for the assumption of a nerve net. These 

 connexions in many places pass directly from the ectoderm, through the 

 mesogloea, to the endoderm. In connecting the ectodermic with the 

 endodermic systems, the lips and probably the oesophagus are not as 

 important as many other parts of the body. 



Notwithstanding the generally diffuse condition of the transmission 

 system in Metridium, there is evidence also for a certain degree of 

 specialization in this system. Stimulation of the tentacles by mussel- 

 juice calls forth a gaping of the esophagus (contraction of the trans- 

 verse mesenteric muscles). Stimulation by weak hydrochloric acid calls 

 forth a retraction of the oral disk (contraction of the longitudinal 

 mesenteric muscles). These two forms of response afford good ground 

 not only for the assumption of independent receptors, but for the belief 

 in relatively independent transmission tracts, a first step in the kind of 

 differentiation so characteristic of the nervous organization in the higher 

 animals. 



• Amer. Journ. Physiol., xlii. (1917) pp. 349-58. 



t Journ. Exper. Zool., xxii. (1917) pp. 87-94 (3 figs.). 



