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SCIENCE 



[N. S. Vol. XXV. No. 647 



ofiers exceptionally favorable material for the 

 study of rhythmic pulsation; and to the reac- 

 tions of this species he devotes the greater por- 

 tion of his paper on rhythmical pulsation. In 

 this species he has discovered a new and very 

 interesting way in which rhythmical pulsa- 

 tions may be maintained. In general, in 

 medusEe, the pulsations are originated in the 

 margin, which contains the sense organs and 

 the greater part of the nervous system. If 

 this margin be cut off the central part of the 

 disc does not, in general, continue to contract 

 in sea water. Romanes, however, found that 

 by passing a weak constant current through 

 such an emarginated disc rhythmical contrac- 

 tions could he kept up in Aurelia; and Loeb 

 has found that the central part of both 

 Oonionemus and Polyorchis can be made to 

 pulsate continuously in appropriate chemical 

 solutions, which are different for the two 

 forms. Mayer has found that if in Cassiopea 

 the marginal sense organs are removed, the 

 remainder of the disc does not pulsate in sea 

 water. If from this disc a ring of tissue be 

 cut, or if the disc be cut in other ways, so that 

 a closed circuit of uninjured tissue be left, 

 in which an impulse can pass continuously 

 from one point, around the circuit, to its point 

 of origin, without passing over any portion of 

 its path twice, it still does not pulsate. If, 

 now, a disc which has been cut in this way is 

 strongly stimulated electrically, mechanically 

 or chemically, a wave of contraction starts 

 from the point of stimulation, and passes with 

 constantly diminishing intensity around the 

 circuit. When it reaches its point of origin 

 it is suddenly reinforced, and starts around 

 the circuit again with renewed vigor. In 

 this way a perfectly regular series of contrac- 

 tions is originated which keeps up indefi- 

 nitely. The rate at which these contractions 

 follow each other depends upon the length of 

 the path from the point of origin around the 

 circuit and back again. If, now, during such 

 a series of pulsations, the ring of muscular 

 tissue be cut across so that there is no longer 

 a closed circuit, the pulsations stop instantly. 

 . Thfe point from which the pulsations start 

 does not always remain at the original point 



of stimulation, but may shift to some other 

 place. In such cases, and when the series of 

 pulsations has been started by an unlocalized 

 stimulus, there is a decided tendency for the 

 point of origin of the pulsations to be located 

 in the geometrical axis of symmetry of the 

 fig-ure into which the disc has been cut. 



Although Dr. Mayer does not discuss this 

 point, phenomena of this kind have a special 

 interest for us on account of the analogy 

 which they may furnish for some of the 

 processes going on in the central nervous sys- 

 tem; and for these reasons it is to be hoped 

 that the cause for the characteristic location 

 of the point of origin of the pulsations, the 

 nature of the reinforcement given to the 

 wave of contraction, the nature of the recip- 

 rocal influence of two points of origin on 

 each other, and similar questions will be still 

 farther studied. 



Many other questions, which it will be im- 

 possible to discuss here, are also investigated. 

 Among them the role of the various salts of 

 the sea water in stimulating and inhibiting 

 the pulsations is considered, but as these 

 chemical questions are not considered from the 

 point of view of the modern general physi- 

 ology, which is based upon physical chem- 

 istry, they are less satisfactory than other por- 

 tions of the paper. Frank W. Bancroft 



SCIENTIFIC JOURNALS AND ARTICLES 

 The Journal of Experimental Zoology, Vol. 

 IV., No. 1, February, 1907, contains the fol- 

 lowing papers : 'Abnormal Development of 

 Toad Ova Fertilized by Spermatozoa exposed 

 to the Roentgen Rays,' by Charles R. Bardeen. 

 ' An Ecological and Experimental Study of 

 Sarcophagidse with Relation to Lake Beach 

 Debris,' by William B. Herms. This is a 

 study of the conditions presented by the flesh- 

 feeding fly-larvae, and the adaptations which 

 have resulted from a certain amount of isola- 

 tion and apparently fairly regular periodicity 

 of food (fish) supply in the particular locality 

 studied, and determination of minimum food 

 supply required for the maturity of indivi- 

 duals as well as the optimum and maximum 

 periods of feeding. ' Rejuvenescence as the 



