192 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
of the strife, which are altogether similar to those which are to be seen 
at the intersections of the filaments of the network. The cuticle can be 
regenerated when it has been accidentally removed from any part of the 
body. 
The hypodermis is a true cylindrical epithelium formed of three 
sets of cells — superficial, intermediate, and basal ; they inclose a number 
of unicellular glands, which are of two kinds, varying with the character 
of the secretion which they pour out on to the surface of the body by 
means of the small canals which perforate the cuticle. The substance 
secreted by the glands has certainly the function of stopping evaporation 
and maintaining humidity, while the mucus serves as a kind of cement 
for the walls of the galleries which these worms excavate. 
The clitellum is a complicated organ, and in the ventral part, which 
should he distinguished from the dorsal, the genital groove and the pads 
of the groove should be noted ; each of these last is divisible into an 
anterior and a posterior portion. A great deal of observation might 
profitably be devoted to this organ, the function of which is almost 
unknown. It is very probable that the pads of the groove become more 
prominent at the time of copulation, in consequence of the contraction 
of the arciform muscles ; the genital groove would then become deeper ; 
and as in copulation worms lie with the pads applied to one another, the 
grooves of the pair would form a canal through which the sperm might run. 
The muscular system is divisible into the muscular layer of the 
wall of the body, that of the wall of the digestive tract, the muscles of 
the intersegmental septa, and the muscular envelope of the central 
nervous system. But all these parts are connected among themselves. 
In the first set we find, in addition to the circular and longitudinal 
muscles, the arciform muscles which lie only between the sexual orifices 
and the hinder end of the clitellum, and the muscles of the setse. The 
characters of the muscular element of the earthworm, which are always 
the same, can be best studied in a piece of the gizzard. It exhibits a 
longitudinal striation, and at certain points one can distinguish a trans 
verse striation ; the striae are not simple lines, but are moniliform, being 
due to a number of swellings connected wfith one another by more 
delicate parts. The author deals in a very detailed manner with the 
muscular system. 
The peritoneal membrane, seen from the surface, has the appearance 
of a pavement epithelium ; the cells which form it are polygonal ; in 
section they are flattened ; those near the longitudinal muscles have 
their protoplasm fusing insensibly wdth the intercolumnar granulated 
substance. Nuclei of various sizes are seen, and some nuclei had several 
smaller nucleoli in addition to the large one. 
The appearances seen justify the belief that direct nuclear division 
was going on in these cells ; there were no certain indications of patho- 
logical degeneration or of processes of fusion. In more than twenty 
cases which were examined essentially similar phenomena were observed. 
Further investigations, however, are necessary, and fresh specimens will 
have to be studied. 
Megascolex caeruleus.* — Prof. A. G. Bourne gives an account of 
this earthworm from Ceylon, and proposes a theory of the course of the 
* Quart. Journ. Micr. Sci., xxxii. (1801) pp. 47-87 (4 pis.). 
