102 LIVERPOOL BIOLOGICAL SOCIETY. 
detected in the parts attached to the anterior body-wall. 
An exactly similar mass of tissue may be found on the 
ventral body-wall on either side of the median line; it 
differs only in its greater development from the modified 
epithelium of the outer aspect of the fold. The cells are 
most numerous in its peripheral portion, the part nearest 
the sub-epithelial tissue consisting almost entirely of fibres 
running in all directions. When in a section many of 
these fibres are cut across, they give rise to a granular 
appearance. Although I have looked through my sections, 
I have not noticed any fibres given off from it, either 
singly or as a bundle, but whether that is from want of 
care in observation, or from defective preparation, I am 
unable to say. 
It is interesting to compare the condition of this 
modified epithelium in Crania with the corresponding 
tissue in the arms of Lingula anatina. From-the greater 
size of the animal it is there larger and easier of detection. 
The cells and fibres throughout the cartilage are very 
numerous (Pl. III., fig. 2). There are three regions of 
especially modified tissue on the arms; one at the outer 
base of the fold, large and deep (PI. III., fig. 2, z.); this 
is connected with the epithelium of the tentacles by fibres 
passing from one to the other; the fibres from the fold 
enter the epithelium of the tentacles and pass as strands 
along its length (Pl. V., fig. 1). Another mass of tissue 
may be found on the ‘‘posterior”’ or “‘lateral’’ canal (PI. 
IIL., fig. 1, w.z.); it is shallow and but slightly developed, 
except at the base of the arms, and it is only in the 
latter region that fibres pass from it into the sub-epithelial 
tissue, and thence to the brachial muscle, where they 
become’ lost (Pl; TIL ‘hes tay, and Ply Vito 27): 
A corresponding tract of tissue does not apparently exist 
in Cramia; and neither of the masses described in Lingula 
