ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 129 



Sense-organs and Regeneration in Cassiopea.* — L. Gary has 

 made a series of experiments to determine the influence of the marginal 

 sense-organs on the rate of regeneration in Cassiopea xamachana. 

 These Medusae, with their nearly flat circular disks with sixteen equally 

 spaced sense-organs, were found to withstand practically any operation, 

 and to retain their vitality indefinitely in a medium-sized jar of 

 sea-water. Experiments were made with entire disks from which all 

 the sense-organs were removed, or with one half the organs removed, or 

 with all but one removed, and so on. Full details of the experiments 

 are given. The author concludes that his study of the influence of the 

 sense-organs on general metabolism — as indicated by CO, production 

 — shows that the metabolism of Cassiopea is influenced by the sense 

 organs in a manner quite in accord with the differences in the rates of 

 regeneration under the several sets of experimental conditions. The 

 rate of regeneration is simply one expression of the general metabolic 

 activity, and as such is subject, like many other activities, to the 

 influence of the nerve centres. 



Neuromuscular Arrangements in Sea-Anemones.f — G. X. Parker 



notes that the glandular, ciliary, and nematocyst systems are local in 

 their reactions to environmental change, and remain normally responsive 

 in animals anaesthetized with magnesium sulphate or chloretone. 

 There is good reason to assume, therefore, that they are not under 

 nervous influence. The muscular system, on the other hand, is so 

 controlled. In Metridium marginatum there are at least thirteen 

 muscles or groups of muscles. Two of these are ectodermic ; (1) the 

 longitudinal muscle of the tentacles, and (2) the radial muscle of the 

 oral disk. The remaining eleven muscles are endodermic : (3) the 

 circular muscle of the tentacles, (4) of the oral disk, (5) of the 

 oesophagus, (G) the sphincter, (7) the circular muscle of the column, 

 (8) of the pedal disk ; the five mesenteric muscles : — ('.)) basilar, 

 (10) longitudinal, (11) transverse, (12) parietal, and (13) the longitudinal 

 muscles of the acontia. 



The nervous mechanism is a network of neurofibrils and the like 

 which permeates the deeper regions of the ectoderm and endoderm. 

 Vigorous stimulation of almost any part of the surface is commonly and 

 quickly followed by the com])lete contraction of the whole animal, and 

 the response is very protracted. 



The simplest type of muscular activity is seen in the longitudinal 

 muscle of the acontium. It is brought into action by the direct 

 application of an appropriate mechanical or chemical stimulus, and is 

 without nervous connexions. 



A second type is seen in the circular muscle of the column, which is 

 open to direct stimulation, and is also under the control of nerves. In 

 this respect it resembles the sphincter pupill;^ of the vertebrate eye, 

 which responds not only to nerve impulses but also directly to light. 



A third type is seen in the longitudinal muscles of the mesenteries, 



* Journ. Exper. Zool., xxi. (1916) pp. 1-32 (11 figs.), 

 t Proc. Amer. Phil. Soc, Iv. (1916) pp. 340-3. 



Feb. 31st, 1917 K 



