LIFE-HISTORY OF BUCEPHALUS HAIMEANUS. 655 
the long axis of the body, the crease or depression between 
each row causing the lines which give the impression of 
longitudinal striation, while the cross-lines, which are not 
continuous (fig. 31), and which are heavier, i.e. of greater 
breadth, are caused by the spines themselves. 
The arrangement of the muscle-fibres immediately below 
the cuticle may add to the effect. 
T am led to the view above expressed by the appearance in 
the most mature cercariz that I have obtained. In these the 
longitudinal striation had disappeared, while the cross stria- 
tion, which was still noticeable, was plainly seen to be due to 
the spines, whose ends projected above the general level of 
the cuticle. 
I have never seen nuclei in the cuticle. Ziegler (7) has 
often been quoted by investigators desirous of obtaining 
support for one of the views of the nature of the outer 
covering of Trematodes, as describing nuclei in the Haut- 
schicht of B. polymorphus. On p. 543 (loc. cit.) he says 
that he has seen nuclei in only one section, a section which 
passed tangentially through the integument. Later in his 
paper (p. 547) he speaks of the possibility of error in the 
observations of investigators who have described nuclei in 
the cuticle. 
A comparison of Ziegler’s figure with my own tangential 
sections convinces me that his section really passed so deeply 
as to include some of the nuclei of the parenchymatous tissue, 
lying beneath the cuticle. 
It is not my purpose to review the literature bearing upon 
the much disputed question of the nature of the Hautschicht 
or investing membrane or cuticle of Trematodes. Such reviews 
may be found in nearly all the German publications on the 
subject. A most excellent and recent synopsis may be found 
in Maclaren’s (42) paper. 
Suffice it to say that there have been three major views as 
to the nature of this outer layer. They may be classified as 
follows : 
1. It is a metamorphosed cellular epidermis. 
