Histology. — "On the Determination of Polarity in the Epidermal 

 Ciliated cell. {After experiments on Amphibian Larvae)". By 

 Dr. M. W. WoERDEMAN. (ComiTiunicated by Prof. L. Bolk). 



(Communicated at the meeting of September 29, 1923). 



It is a well-known fact that in tiie early stages of their life the 

 larvae of amphibians have an epidermis, provided with ciliated cells. 

 This cannot be observed distinctly in all species, for they differ largely 

 as to the number of ciliated cells. Nor are these cells evenly distributed 

 over the epidermis of one and the same larva; there are spots where 

 they are scattered thickly, while they occur more sparsely in other 

 spots. 



The ciliary movement canSses a slow rotation of the larvae while 

 the latter are still inclosed in their jelly-like envelope. When this 

 envelope is removed, the exposed larvae will be seen to keep up 

 their rotatory motion owing to the ciliary movement, just as the 

 larvae that have already left their envelope. At the same time a 

 rather violent current may be observed in the water encircling the 

 larva. It is self-evident that this current is strongest where most 

 ciliated cells are collected. Strong currents are, therefore, distinguishable 

 along certain parts of the larval body, weaker streams along other 

 parts, which e.g. have been minutely examined by Assheton ') for 

 Rana temporaria and Triton cristatus and have been represented in 

 plates for larvae of various age-periods. 



It appears that in these animals the first action of cilia is noticeable 

 in larvae where the neural folds are still open, shortly before their 

 closure. There is a strong cnireni in the water round about the 

 larva from head to tail along the neuial walls. My own researches 

 were made on Rana esculenta and Triton alpestris larvae. I found 

 that in these amphibians the ciliary movement begins when the 

 neural walls are in part united. The direction of the fluid-streams 

 along the larval body 1 found to agree in the main with Assheton's 

 schemata, although there were also some differences. This, 

 however, is not to the purpose. The direction of the ciliary move- 

 ment in normal larvae of Rana esculenta and Triton alpestris was, 



'I R. AssHETON. Quarterly Jouni. of inicr. Science New Series. Vol. 38. 1896, 

 p. 465. 



