ANATOMY AND HISTOLOGY OF PLEUROCHATA MOSELEYI. 505 
- differ slightly in size, the larger measuring 3°9 c. in length and 1°85 c. in 
breadth, and the smaller 3:1 c. in length and 1'9 cc. in breadth. The cocoons 
_ are glassy in appearance and of a dull bottle-green colour, the smaller specimen 
with three bands of a darker green at one end, the larger specimen of a uniform 
colour. Each cocoon appeared to have two openings, one at each end; the 
anterior opening was obvious, but of the existence of the other I was not 
quite able to satisfy myself. The chitinous wall of the cocoon exhibits no 
particular structure. Plate X XVII. fig. 12 represents one of the cocoons of 
the natural size. The larger cocoon was opened, and contained two embryos 
slightly folded upon each other, as shown in fig. 11, and surrounded by a 
quantity of firm coagulated matter, which no doubt is the remains of the 
food yolk. The embryos lie, as represented in the figure, with their anterior 
extremities towards the orifice of the cocoon. The two embryos separated 
from each other, and entirely freed from the food yolk, are shown in figs. 
6, 7. One of these two was selected for study, but my time was unfor- 
tunately limited, so that only a few points in its structure were made out. 
The first thing to which my attention was directed, was naturally the distribu- 
tion of the sete, but the embryos were so far advanced that the setz were. 
present in their full number, and with the characteristic distribution found in 
the adult (Plate XXVII. fig. 15). Fig. 13 of the same plate represents a vertical 
section through the body wall in the dorsal region, where the longitudinal 
muscular coat ¢’ undergoes a curious alteration ; instead of the fibres being 
arranged in compartments separated by trabecule of fibrous tissue, as in other 
parts of the body, there is a network of connective tissue, which has very much 
the appearance of the reticulum of fat, and which at the two sides becomes 
gradually continuous with the fibrous trabecule; about the middle of this 
reticulum is a single line of muscular fibres, which appear to be of a somewhat 
greater diameter than those in the other parts of the longitudinal coat. The 
circular coat undergoes also an alteration in this region; the fibres are more 
wavy, and less regular in their arrangement; this is displayed also in fig. 16, 
which represents a strip of the skin torn off and examined entire ; moreover, 
the changes undergone by the two muscular coats are shared by the epithelium 
and by the cuticle, both of which are increased considerably in thickness. 
- What the meaning of this is I cannot guess, neither had I any time to re- 
examine the adult to see if there was the same alteration of structure on the 
dorsal surface; since, however, this band was perfectly visible to the naked 
eye, and as there was no such difference apparent in the adult it would seem 
after all to be-peculiar to the young specimen. 
VOL. XXX, PART II. = 4 
