514 FRANK E. BEDDARD. 
tures known to me in an earthworm with which they may 
possibly be compared are the peculiar integumental cells of 
Urocheta; but these latter lie at the base of the epidermis 
instead of at the summit as in Acanthodrilus. One is 
usually inclined to regard a modified epidermic cell as a 
sense-organ, but there is no evidence that the bodies in 
question have a sensory function. On the other hand, they 
cannot be compared with the gland-cells of the epidermis. 
The cavity lying beneath each cell is very curious, and fits 
with the possibility of their being dioptric media ; they are not, 
however, specially transparent, judging at least from their 
appearance when preserved. At present I think the nature of 
the cells must be left unsolved. 
§ Gonads. 
The development of the gonads in Lumbricus has been 
studied by Bergh (11), who has made known some interesting 
facts as to the number originally present. The adult Lum- 
bricus has two pairs of testes depending from the anterior 
septum of Segments 10 and 11, and a single pair of ovaries 
occupying a corresponding position in Segment 13. In the 
embryo, however, the 12th segment possesses a pair of gonads 
also, which appear never to advance beyond a very rudimentary 
stage. 
I find in Acanthodrilus that there are originally four 
pairs of gonads present, which are in Segments 10, 11, 12, and 
13; but these, instead of being attached to the front wall of 
their segment, as in Lumbricus, are attached to the poste- 
rior wall. This is the case with the adult worm, as I have 
satisfied myself by the dissection of a large specimen. Acan- 
thodrilus annectens, therefore, is not the only example 
known of this anomalous condition. The gonad of the 12th 
segment in Acanthodrilus is, however, at first as fully 
developed as any of the others; it contains, as they do, large 
germinal cells, with the peculiar nuclei which characterise 
these cells. These nuclei (fig. 14) are limited by a distinct 
and darkly staining membrane, against which are closely 
