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SCIENCE 



[N. S. Vol. XXIX. No. 741 



or " orderly beings," may be applied. These forms 

 are held to be due to some fundamental cause 

 inherent in the germ itself, that is, in the egg 

 or the embryo in the early cleavage stages, and 

 must be carefully distinguished from all deformi- 

 ties or other monstrosities that are due to external 

 or later developing causes, not germinal. 



A Further Contribution on the Regenerative 

 Power of the Somatio Cells of Sponges aper 

 Removal from the Parent: H. V. Wilson, Uni- 

 versity of North Carolina. 



I have described (Joum. Exper. Zool., Vol. V., 

 No. 2) a method by which sponges, more partic- 

 ularly Microciona, may be made to regenerate 

 from somatic cells. The sponge is cut into pieces 

 and the pieces are strained under pressure through 

 bolting cloth. The separated cells of the body pass 

 through the pores of the cloth and collect as a 

 sediment on the bottom of the dish. The sediment 

 may be drawn up into a pipette and strewn over 

 a glass slide or other object. The cells combine, 

 forming a plasmodial structure which gradually 

 differentiates into a functional sponge having 

 pores, oscula, flagellated chambers and canals. It 

 remained doubtful whether sponges grown in this 

 way would live long enough to develop the char- 

 acteristic skeleton. The experiments with Micro- 

 ciona have been repeated, and the regenerated 

 sponges kept for two months. The characteristic 

 species-skeleton was differentiated. Reproductive 

 elements and embryos were also formed. The 

 sponges appear to be healthy and to differ in no 

 wise from normal specimens. 



The Effects of Certain Paralyzing Agents on 

 Form Regulation: C. M. Child, University of 

 Chicago. 



The Rate of Regeneration and the Effect of New 



Tissue on the Old Body: Chables R. Stockabd, 



Cornell Medical School. 



Regeneration takes place equally fast from the 

 disk of Cassiopea wamachana, whether it be in 

 periodic pulsation or in a condition of rest. 



Peripheral pieces of the disk cut in sundry pat- 

 terns show decided regulatory ability and tend to 

 assume the original circular shape of the entire 

 disk in the most direct way that their forms will 

 permit. The attainment of the circular form in- 

 hibits the process of regeneration in the pieces, 

 yet regeneration will continue for a much longer 

 time if such shapes be prevented. 



The rate of regeneration from a peripheral cut 

 on the Cassiopea disk is faster the nearer the disk 

 center the cut is made. In the brittle-stars Ophio- 



comu riisei and 0. echinata new arms regenerate 

 faster as the old arms are cut off nearer their 

 base of attachment to the body-disk. 



The rate of regeneration does not bear a definite 

 relation to the extent of injury in all animal spe- 

 cies. The medusa, Cassiopea, regenerates each 

 oral-arm at a rate which is independent of the 

 degree of injury when replacing either one, two, 

 four or six of its arms. If, however, eight arms 

 are amputated each arm regenerates at a rate 

 significantly faster than the rate when injured to 

 any less degree. Ophiocoma riisei regenerates one, 

 two, three, four or all five of its arms at rates 

 not significantly different. 0. echinata grows in- 

 dividual arms fastest when only a single arm is 

 regenerating and successively slower when two, 

 three, four and five arms are being replaced. 



Regenerating tissue possesses an excessive ca- 

 pacity for the absorption of nutriment and may 

 do so even to the detriment of the old body tissue. 

 The unfed disk of Cassiopea decreases in size in 

 direct relation to the number of regenerating 

 arms. Although the disk regenerating eight new 

 arms is growing them at the most rapid rate, it 

 is, nevertheless, decreasing in size most rapidly. 

 In growing specimens of Ophiocoma riisei the 

 increase in size is slower in those individuals 

 regenerating many arms as compared with others 

 regenerating fewer. 0. echinata regenerates each 

 arm faster when only a few arms are cut, such 

 individuals increase in size at about the same rate 

 as do those which are regenerating each arm 

 slower although more arms are being replaced. 



Successive Regenerations; New Observations and 

 General Discussion: Chaeles Zelent, Univer- 

 sity of Indiana. 



Tlie Physiology of Nematocysts: O. C. Glaser 



and C. M. Spaeeow, University of Michigan. 



Nematocysts, isolated by digestion and macera- 

 tion, can be discharged by raising their internal 

 pressure. 



The pressure needed to bring about explosion 

 varies with conditions. It may be artificially 

 altered by immersion in various liquids, a fact 

 which explains why the nematocysts of eolids 

 explode in sea water, whereas those freshly iso- 

 lated from coelenterates, do not. 



When stimulated, the nematocyte is a factor in 

 the discharge of the thread. It is not possible to 

 show that stimulation of the mother-cell results 

 from all the conditions under which explosion 

 occurs. Nevertheless, it is probably true that 

 when a nematocyst discharges as the result of 

 conditions normal to the lives of ccelenterates, it 



