234 



Mr. J. N. Langley. Variations of 



[Nov. 19, 



be seen, for at any rate a plastoid is not present. A somewhat casual 

 examination was also made of many organs of movement, but in tbem 

 no plastoid was observed. In Drosera rotundifolia and otber species 

 plastoids occur which resemble those of Drosera dichotoma. Strong 

 single induction shocks or tetanising currents cause the plastoid to 

 assume the spherical condition, or very frequently to break up into a 

 string of small spheres. A sudden blow on the cover slip also causes 

 the assumption of the spherical form. . Moderately strong tetanising 

 shocks cause swelling of the protoplasm, and increase of rapidity of 

 movement and granularity. Very strong shocks may cause the con- 

 traction of the primordial utricle from the cell- wall at certain small 

 areas, but immediate death always ensues, since the stimulus required 

 is abnormally great. The normal effect of a regulated stimulus is to 

 induce a swelling of the protoplasm and a loss of turgidity, and in 

 consequence of the unequal reaction of the various cells to such a 

 stimulus, movement of the tentacle also occurs. 



[Note. — I have decided to name the body which I have provision- 

 ally spoken of as the plastoid "the rabdoid " (Gk. rabdos, a stick or 

 wand). The change in form of the rabdoid appears to be a con- 

 sequence of the molecular changes in the protoplasm. Differences of 

 turgidity are among the results of these changes. — Nov. 28, 1885.] 



VI. " On Variations in the Amount and Distribution of Fat in 

 the Liver-Cells of the Frog." By J. N. Langley, M.A., 

 F.R.S., Lecturer on Histology in the University of Cam- 

 bridge. Received September 23, 1885. 



I have in a previous paper* mentioned some of the changes which 

 occur in certain circumstances in the number and arrangement of the 

 fat-globules in the liver-cells of the frog. From observations made 

 since that time at different seasons of the year, I have been able to 

 ascertain certain points undetermined in the previous account. 



Variations in the Amount and Distribution of Fat with the time of 

 Year. — The fat in the liver-cells is at its maximum amount in Feb- 

 ruary and March. In January it is, as a rule, somewhat less. In 

 April it rapidly decreases ; from May until December it is present in 

 comparatively small though varying amount. It is usually present 

 in minimum amount in September and October. 



Generally speaking, the fat-globules form an inner zone in frogs 

 which have hungered more than a week. In January, February, and 

 March, however, the fat-globules are commonly more numerous in 

 the outer part of the cells, often forming a distinct outer zone. 



* " Proc. Roy. Soc." vol. 34, p. 20. 



