ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 381 



the character of the latter, and the method of its construction. In 

 its earliest stages it is a transparent, smooth, and homogeneous slime- 

 like excretion, within which the worm may be very clearly seen, as it 

 works its way forward or drags itself backward by means of its pedal 

 hooks and spines. Later on, the anterior extremity thickens and 

 becomes more and more opaque, and, as Dr. Leidy has observed, 

 "feebly annulated," presumably from the adherence of effete 

 particles, and their compression by the repeated withdrawal of the 

 ciliated tentacles into the mouth of the tube. This method of pro- 

 longation must continue during the residence of the worm, and in 

 consequence, if supported, it may sometimes reach a length which is 

 several times that of its inhabitant. 



Miss S. G. Foulke has also examined * the worm and describes the 

 pulsation of the green tentacles. 



To ascertain how long the cilia upon the tentacles would continue 

 their motion after separation from the body of the worm, both lopho- 

 phores of an adult were cut off above their junction. 



At first the tentacles remained closed from the shock, but soon 

 they were expanded, the cilia displaying active motion, and presently 

 the two separated lophophores began to move about in the zoophyte 

 trough. This motion was produced by the action of the tentacles, 

 which bent in all directions, the tips touching the glass, and was not 

 a result of the currents produced by the cilia. In a few minutes one 

 lophophore had crawled in this manner quite across the trough, while 

 the other remained floating in the water near its first position. In 

 the case of this latter the motion was produced by the ciliary currents, 

 and was entirely distinct from the crawling above noted. During 

 this time the decapitated worm had sunk to the bottom, and, though 

 turning and twisting a good deal, did not attempt to protrude the 

 mutilated support of the lophophores. Its body was so much con- 

 tracted that the segments were not above one-third their usual size. 



At the end of five hours the worm was apparently dead, numbers 

 of infusoria had collected to prey upon it, and the surface of the body 

 presented a roughened appearance as though covered with tubercles. 

 The lophophores were still crawling and swimming about. At the 

 end of the eighth hour the lophophores had ceased to crawl, but the 

 ciliary action, though feeble and uncertain, still continued. The 

 body of the worm was then covered with a thick fungoid growth, 

 consisting of transparent rod-like filaments 3/16 in. in length ; some 

 of the filaments presented a beaded appearance. All motion of the 

 cilia upon the tentacles had ceased, and these also were being devoured 

 by infusoria. 



Life-History of Thalassema.f — H. W. Conn describes (in a pre- 

 liminary paper) the early stages of development of Thalassema melUta 

 that inhabits empty " sand-dollar shells." Its anatomy is much the same 

 as that of Echiurus described by Sprengel. It is dioecious. The ova 

 and mother-cells of spermatozoa are simply modified cells of the 

 peritoneal lining of the body-cavity, in which, whilst developing, they 



* Proc. Acad. Nat. Sci. Philad., 1884, pp. 48-49. 



t Stud. Biol, Lab. Johns Hopkins Univ., iii. (1884) pp. 29-35 (1 pi.). 



