ON TEMNOCEPHALA. . 285 



of muscular fibres, longitudinal layer of muscle, nervous 

 layer. 



The cuticle (Plate XXI, fig. 1, c.) attains a thickness of 

 •006 mm. in T. fasciata. It is beset with numerous vertical 

 pore-canals, the presence of which gives it the appearance in 

 sections of being made up of close-set papilhe. On a surface 

 view it appears slightly corrugated, the rugae being exceedingly 

 minute, irregular, and mostly transverse. 



The epidermis (e) is of nearly equal thickness with the 

 cuticle. It is composed of a thin layer of protoplasm, with 

 regularly distributed nuclei, but without a trace of cell- 

 boundaries. The nuclei are spherical, of a diameter nearly 

 equal to the whole thickness of the epidermal layer, and with 

 a finely granular interior. In vertical section the substance 

 of the epidermal layer appears to be divided into a series of 

 vertical columns by a number of parallel lines. This appear- 

 ance is produced by the presence of very numerous pore- 

 canals, which run perpendicularly through both epidermis and 

 cuticle to open on the surface of the latter ; and a surface view 

 of the epidermis shows the numerous and closely-placed 

 rounded openings. In T. minor the cuticle is smooth, and 

 the nuclei in the epidermis much less numerous than in T. 

 fasciata. 



The basement membrane (b.) on which the epidermis 

 rests is a perfectly homogeneous membrane of, comparatively, 

 considerable thickness, being as thick as the epidermis itself. 

 It stains deeply with carmine dyes — much more deeply than 

 the epidermis, but is not readily stained with hematoxylin. 

 It is devoid of nuclei or other evidence of structure ; like the 

 superficial layers it is perforated by the pore-canals, but it is 

 difficult to see them unless in parts where the secretion of the 

 subcutaneous glands, which is readily acted on by staining 

 agents, is passing out. Like the cuticle and epidermis the 

 basement membrane varies little in thickness in different parts 

 of the body. In T. minor cuticle, epidermis, and basement 

 membrane are very delicate, and together are only *008 mm. 

 in thickness. 



VOL. XXVIII, PART 2. NEW SER. U 



