vT~- 
NOTES ON THE STRUCTURE OF OIKOPLEURA. 53 
and the right lateral lobe of the testis until it reaches the 
ventral surface between the stomach and the anterior end 
of the ovary (Pl. I. fig. 9). It now turns forwards, reaches 
the base of the tail, enlarges to form the caudal ganglion, 
and then continues onwards through the length of the 
tail lying on the left side of the notochord. 
I have not discussed specially those detailed points in 
which the preceding account differs from those of Fol, 
Hisen and other authors. The new method of investigation, 
serial sections in place of transparent objects, might be 
naturally expected to yield some new results in matters of 
detail: besides I cannot be certain that my form is speci- 
fically identical with any of those previously described. I 
may mention, however, as perhaps the most interesting 
points shown in my figures :—the condition of the endo- 
style as a diverticulum to a great extent shut off from 
the branchial sac, the presence of a genital duct, the distri- 
bution of the enlarged ectoderm cells and the cuticular 
test, the exact course of the nerve cord through the pos- 
terior part of the body, and finally the shapes and relative 
positions of the alimentary and reproductive viscera. 
EXPLANATION OF THE PLATES. 
All the figures with the exception of fig. 9 on Pl. IV. 
were drawn from the sections, which were placed so that 
right and left sides of the figure represent right and left 
sides of the animal. With the exceptions of figs. 4, 5, and 
8 on Pl. I. figs. 9 and 10 on Pl. III. and figs. 6 and 8 on 
Pl. IV. which show more highly magnified details, all the 
figures were drawn under a moderate magnification, about 
115 diameters. ‘The following abbreviations are used :— 
