138 PROTOPLASM 



it might well have arisen by modification of the alveolar 

 framework of the cells of the epidermis. 



I take this opportunity to remark, that the much 

 thicker cuticle of PJiascolosoma elongatum also frequently 

 shows the same structure and very plainly either in trans- 

 verse or longitudinal section ; only, corresponding to its 

 greater thickness, the number of its layers is much more 

 considerable. 



Cuticle and so-called hooks of Distomum hepaticum. In 

 very fine sections of specimens of this Trematode preserved 

 with picro-sulphuric acid, and then stained very intensely 

 with iron-haematoxylin, the following details can be made 

 out as to the structure of the cuticula. The whole cuticle 

 stains very intensely, the cuticle proper more violet, while 

 the hooks lying in it stain a beautiful blue. The external 

 half of the cuticle shows, however, a rather more dirty violet 

 tint, and the inner portion more bluish violet, which depends 

 without doubt on large quantities of granules, staining a deep 

 blue, and lodged in it. The whole cuticle has a distinct 

 reticular meshed structure, in which the framework has a 

 somewhat blue tint, the intervening matrix, on the other 

 hand, appearing violet, for which reason the colour is violet 

 as a whole (Plate XL Fig. 1). In the hooks the case is 

 otherwise, from the fact that the intervening matrix is also 

 coloured blue, so that they appear blue throughout. The 

 surface of the cuticle is formed of a very distinct dark 

 border of a blue colour, appearing like a pellicle, under 

 which extends a somewhat lighter, radially directed layer of 

 meshes, which possesses entirely the characters of a marginal 

 alveolar layer. The external half of the cuticle shows in its 

 remaining parts an irregular framework of meshes, which 

 obtains the appearance of radially directed fibres the more 

 it approaches the internal half, this character being quite 

 pronounced in the latter region. In addition, numerous 

 granules, stained a very intense blue, are lodged in the 

 nodal points of the framework of this deeper portion. 

 Since these nodal points, and therefore the granules also, lie 

 one behind the other, in more or less distinct rows, in conse- 

 quence of the fibrillar arrangement of the meshwork, the 



