Massie, Skin of the Tadpole. g 



at the stage just preceding the appearance of the front legs) has 

 described them as nerve termini. He has postulated a theory 

 which runs somewhat as follows : Each cell of the epithelium 

 is supplied with two nerve fibres, one sensory, the other motor, 

 which end free in little knobs within the cell. When the cells 

 divide these nerve fibres divide also, so that each new cell is 

 supplied with a branch from both the primitive motor and the 

 primitive sensory nerve. 



But under favorable circumstances with thin and carefully 

 prepared sections by close examination these peculiar nerve-like 

 structures can be distinguished from nerves. For, although 

 they react with some stains like nerves, with others they give a 

 different color ; moreover they are too large for nerves and, so 

 far as we could see after examining a great many sections differ- 

 ently stained, they lie wholly within the cell-walls. They are 

 never seen in the ental cells of the Malphigian layer but are 

 confined to the members of the ectal series. We would there- 

 fore say that they are not nerves, but fibres of linin or chroma- 

 tin, which serve a special purpose in preparation for rapid sub- 

 division at the time of the metamorphosis. This view receives 

 confirmation from the fact mentioned by Pfitzner that these fila- 

 ments are more conspicuous at this stage than at any other, and 

 also from the fact that at this stage there is a rapid subdivision 

 of cells of the ectal layer to form a second row of cells in the 

 horny layer. The latter unquestionably springs from the cells 

 of the ectal layer only. At this time the intra-cellular skeins 

 often break up and assume forms strongly suggesting mitotic 

 figures. (Fig. 2.) We believe therefore that the ectal cells of 

 the Malphigian layer have a different function from the ental 

 cells. The latter form the glands and at an older stage rapidly 

 shrink in size. The former supply the horny layer with new 

 cells and the peculiar thread-like bodies within them have an 

 active part to play in cell-division. 



After examining much material prepared in different ways, 

 we believe that the nerve bundles from the central nervous sys- 

 tem send out toward the skin medullated nerves which on reach- 

 ing the closely compacted middle layer of the corium run 



