524 



SCIENCE. 



[N. S. Vol. XXIII. No. 588. 



less widely from normal embryos and 

 larvffi. 



Differentiation of the egg does not occur 

 in the absence of cleavage, and all ciliated 

 bodies observed, whether normal or ab- 

 normal, possess a cellular structure. 



The Eeimbahn of Chrysemys: Bennett M. 



Allen. 

 Morphology of Coeloplana: J. F. Abbott, 



Washington University. 



Ample material was rediscovered in Ja- 

 pan. Careful histological study shows that 

 contrary to frequently expressed opinion 

 Cceloplana has practically no planarian af- 

 finities and can not be considered a primi- 

 tive form, but rather a highly specialized 

 ctenophore. The adoption of littoral hab- 

 its has produced great divergence from the 

 typical organization of ctenophores. On 

 the other hand, there are many points of 

 structure characteristic of pelagic Cteno- 

 phora that are retained in Cceloplana as 

 vestigial structures, apparently useless to 

 a crawling animal, but indicating a pelagic 

 origin. Among the points worked out in 

 Coeloplana new to ctenophore morphology 

 are the development of respiratory dorsal 

 tentacles, the normal sloughing off of di- 

 gestive epithelium from the gastric canals 

 and a method of origin of the adhesive cells 

 of the tentacles at variance with the de- 

 scriptions of other investigators. 



The Origin of the Proglottids in the Ces- 

 tode Crossobothrium laciniatum: W. C. 

 Curtis, University of Missouri. 

 The method accepted as the universal 

 one by which the proglottids of a cestode 

 originate, does not obtain in the species C. 

 laciniatum. This cestode, instead of form- 

 ing its proglottids by the appearance of 

 each new one between the seolex and the 

 most anterior proglottid of the chain, 

 shows the proglottids originating in the 

 following manner : there appear at the pos- 

 terior end of the young worm segments 



which we will term the 'posterior proglot- 

 tids.' These extend over about the pos- 

 terior fourth of the body and arise from 

 behind forward after the manner described 

 for other cestodes. When about fifty 

 such 'posterior proglottids' have appeared, 

 others, which we will term the 'anterior 

 proglottids, ' begin to develop in the region 

 just behind the seolex. These 'anterior 

 proglottids' appear in the reverse direction 

 so that the oldest is the one next to the 

 seolex. From this time on the worm is, 

 therefore, segmenting from both ends to- 

 ward a point somewhat anterior to the 

 middle of its length. 



The anterior end produces upwards of 

 fifty, the posterior upwards of two hun- 

 dred, proglottids before the two meet and 

 all sign of the transition from one region 

 to the other disappears. 



After reaching such an 'adult' condition, 

 no more proglottids are formed until the 

 ones already in existence have been greatly 

 reduced in numbers by the liberation of 

 motile proglottids from the posterior end. 

 When this reduction has progressed so far 

 that the reproductive organs are beginning 

 to appear well into the region occupied by 

 proglottids which had an anterior origin, 

 the part of the worm between the seolex 

 and the most anterior proglottid elongates 

 into a neck which eventually segments into 

 posterior and then into anterior proglottids 

 as did the young worm. 



The bearing of these facts upon current 

 explanations of the nature of the cestode 

 body will be discussed in a forthcoming 

 paper. 



Some Ohservatiom on Gastropod Nerve 



Cells: W. M. Smallwood and C. G. 



Rogers, Syracuse University. 



This report includes studies on the opis- 



thobranchs, nudibranchs and especially the 



pulmonates, Planorhis and Umax. Many 



cytological observations have already been 



