and Laboratory Methods. 1265 



explain this reaction as a result of the attainment of a position of equal bilateral 

 stimulation by the same sort of contraction processes on the supra-optimally 

 stimulated side as in the other cases. 



The principal conclusion is that : " Light acts in one way, that is, by its inten- 

 sity. The light operates, naturally, on the part of the animal which it reaches. 

 The intensity of the light determines the sense of the response, whether contrac- 

 tile or expansive ; and the place of the response, the part of the body stimulated, 

 determines the ultimate orientation of the animal." Under ordinary circum- 

 stances the part of the body stimulated is, of course, a direct function of the 

 direction of ray. The paper shows clearly that the orienting " photopathic " 

 reaction is very probably the same thing as the response ordinarily known as 

 " phototactic." R. p- 



^ r, ^ , ^, . , r , „, The aim of this work is to determine 



Bardeea, C. R. On the Physiology of the Plan- 

 aria Maciilata with especial reference to the SOme of the internal conditions of 

 Phenomena of Regeneration. Amer. Jour, regeneration in the common flatworm, 

 Physiol. 5: 1-55,1901. ° ., r 



Planaria maculata. 1 he account of 



the regeneration work is prefaced by sections devoted to the general anatomy 

 and physiology of the animal. In the account of the physiology " sensation " is 

 discussed in a very general way. The work of Loeb on the light reactions of the 

 worm is mentioned and a very brief description is given of the reactions to con- 

 tact stimuli. In this section the author makes the surprising statement that he 

 has not found that " the worm is sensitive to anything but light and contact." 

 Under " Movement " two sorts of progression, " swimming " and " crawling," are 

 described. The '' swimming," by which term the author evidently intends to 

 designate the motion of the worm ordinarily spoken of as "gliding," is almost 

 entirely due to the action of the cilia covering the ventral surface of the body. 

 The crawling is an entirely muscular movement brought about by waves of con- 

 traction passing from the anterior to the posterior end. Experiments on the cen- 

 tral nervous system showed that, at any level, it is capable of governing the activ- 

 ities of all parts of the body posterior to that level. Under " Internal Activ- 

 ities " are discussed the processes of deglutition, food-dispersion, defecation and 

 respiration. Food is taken in by peristaltic contractions of the pharynx and then 

 distributed evenly through the branches of the intestine by contractions of the 

 body wall. Digestion is mainly intracellular. Defecation is brought about by a 

 series of sharp contractions of the whole body while the pharynx is held open. 

 There are a few brief and rather loose statements in regard to respiration and 

 excretion. The part of the work devoted to the general physiology of the animal 

 is, on the whole, weak and unsatisfactory. The remainder and larger part of the 

 paper is devoted to a detailed study of the cellular processes taking place during 

 regeneration. Most of the gross forms of regenerated animals which have been 

 obtained by other workers on the same subject are carefully described with refer- 

 ence to the details of their development. The processes occurring after the 

 removal of a part of the animal are briefly as follows : (1) The wound becomes 

 smaller in surface area on account of the contraction of the surrounding muscu- 

 lature. (2) The cut surface remaining is protected by the transformation of the 

 cells directly exposed to the water into mucoid tissue. Later the surface epithe- 



