456 Physiology and Histology o/Convoluta Schultzii. [Mar. 27, 



side of the interior of this cavity and parallel to the long axis of the 

 cell, are a number of distinct transparent homogeneous filaments in- 

 serted above and below into the ordinary granular protoplasm which 

 constitutes the remainder of the cell. This division of the cell into a 

 granular and a fibrillated portion is similar, as Dr. Malassez 

 suggested to me, to that which obtains in the developing muscular 

 cell of a tadpole's tail, and though also somewhat remotely, to the 

 structure described by Lankester in the heart of Appendicularta* In 

 a teased preparation, some of these cells are easily found in a state 

 of rapid rhythmical contraction, giving as many as 100 — 180 energetic 

 beats per minute. The form of the cell alters with every pulsation, 

 shortening and broadening like a contracting muscle. This change 

 of form is simply impressed upon the cell body by the contraction of 

 the internal fibres, and does not therefore truly correspond to that 

 observed in a muscle. Some cells also of extreme curvature (for 

 hardly any two are quite alike) bend sharply and return with a spring. 

 The movements soon become slow and inco-ordinate, and waves can 

 be seen passing along the separate fibres independently of each other. 

 The movement stops altogether and the cell bursts, bat the fibres 

 resist for some time longer the destructive action of the water. 



I have never been able to observe any rhythmical contraction, but 

 at most a feeble quivering within the cell while in the body of the 

 animal, nor to make out any trace of definite arrangement. Max 

 Schultze has described how the alimentary canal of the higher Pla- 

 narians swarms with Opalince, and it is possible that these so singular 

 structures may be excessively modified parasitic Infusoria. In any 

 case, the main histological interest lies in the fact that these pulsatile 

 cells cannot be classified either with ciliary or amoeboid, with plain or 

 striated muscular cells, but present a distinct type of contractile 

 structure. 



In one of these bodies, which had come to rest in the characteristic 

 curved pear-like form, the nucleus-like body, which is often to be 

 seen at one side, was distinctly seen to be in motion. It slowly dived 

 under the contractile filaments, and moved steadily towards the 

 opposite side, displacing the fibres slightly as it pushed its way. 

 When it had reached the middle the cell had straightened into a per- 

 fectly symmetrical pear-shape, and by the time it had reached the 

 opposite side the cell had curved to the same side. After a momentary 

 pause it commenced to go back again, and the oscillation of this 

 singular body along the transverse diameter of the cell, with the 

 accompanying changes of form of the whole, continued with perfect 

 steadiness for at least half an hour, enabling me to draw all the phases 

 again and again. One whole oscillation occupied a little over a minute.f 

 * " Ann, and Mag. IS T at. Hist." 1873, p. 88. 



f Figures will be published in the "Archives de Zoologie Experimentale." 



