786 RECORD OP CURRENT RESEARCHES RELATING TO 



it will be useless here to describe the numerous loops that it makes. 

 As to the minuter details, we are told that the saccule is not a simple 

 sac with smooth walls, but that it consists of a large number of csecal 

 sacs, between which there is a rich network of connective tissue, in 

 the lacunae of which the blood can freely circulate. The cells have 

 large nuclei, and pale, finely granxilar contents ; on the other hand, 

 in the canal the cell-contents are arranged cord-wise, and are best 

 developed on the side of the cell most distant from the lumen. The 

 thick cuticle is likewise striated, and in a direction perpendicular to 

 the axis of the canal. The results of his observations on the green 

 gland of Astacus fluviatilis do not altogether agree with those of 

 previous observers; forming a compact mass, lying largely in the 

 thorax, the saccule and canal are still to be distinguished ; the former 

 is rounded, and of a yellowish-green colour; the canal is delicate, 

 provided with diverticula, and extended into a wide canal of a pale 

 greenish-grey colour, which has similar diverticula, and which lies 

 coiled between the saccule and the green part of the canal ; the 

 terminal portion of the duct is here again lined by a chitinous cuticle. 

 Deep clefts are to be observed between the epithelial cells of the 

 saccule, and the protoplasm is seen to contain a number of amorphous 

 yellow-green bodies; the bright-green portion of the canal has 

 epithelial cells of a cubical or cylindrical foi^m, and the contained 

 granules are arranged cord-wise ; there is a thickish cuticle, thinner 

 at certain points, and so, in optical section, appearing as though it 

 were composed of rods. The author insists on the rich supply of 

 blood-vessels to all parts of the canal. 



When we compare these results with what we know of the shell- 

 gland, we find a striking resemblance in structure; without going 

 here into this subject in detail, attention may be directed to the 

 conclusion that the two glands have a similar structure ; further, the 

 view that they are homologous is supported by the fact that they are 

 both mesodermal in origin. As to the functions of the parts, it 

 would seem that the terminal saccule is to be compared to the 

 Malpighian capsules of the Vertebrate kidney ; while the canals are 

 comparable to the tuhuli contorti. 



In both Vermes and Mollusca the urinary canals are formed by 

 a few cells, and the difference in the length of the canal in Cyclops as 

 compared with Cetocliilus is to be explained by the fact that one 

 inhabits fresh and the other salt water, just as the marine Polychaeta 

 have short, and the fresh-water Oligochaeta long segmental organs. 



Rapidity of the Transmission of Motor Stimuli along the Nerves 

 of the Lobster.* — MM. Fredericq and Vaudevelde find that at Ghent, 

 at a temperature of 10-12'' C. (in February and March), this rapidity 

 was about 6 metres a second ; at Eoscoff, with the temperature at 

 from 18-20° C. they attained different results, the rapidity being 

 from 10-12 metres a second. Both these data show that in the 

 lobster stimuli are conveyed along motor nerves very much more 

 slowly than they are along those of the frog or of man. 



* ' ComptcB Rendus,' xci. (1880) p. 239. 



