33(3 ME. B. E. UNWtN: NOTES UPON THE 



The old cuticle is split transversely in the thin cuticle joining the terga of: 

 the 4th find 5th segments, and then quickly the split extends laterally and 

 ventrally. The creature holding firmly on to the weed with the first 4 pairs 

 ot legs sways the hinder part of its body up and down. This action seems 

 to help in the withdrawal of the legs and other appendages from the old 

 cuticle. I have also noticed that the casting of the hind part is assisted by 

 slowly walking forwards a short distance; the friction of the legs of the old 

 cuticle against the weed of the ground helps the withdrawal. 



I have not been able to detect any other splitting ; each half is a perfect 

 cast of the part of the body from which it comes. Asellus does not, as a 

 rule, eat its cast cuticle. This is the usual procedure in the Oniscoidea. 



Both Wege and Kaulbersz give tables of the interval between two succes- 

 sive moultings, and discuss the effect of various factors, such as food, age, 

 temperature, mutilation, upon this interval. With poor food the intervals 

 average about 24 days; Wege has records varying from 8 to 30 days. The 

 average time under normal conditions is about 3 weeks. The moulting in 

 relation to the sexual processes will be discussed below. 



The sexes are distinct. Full-grown males are much larger than sexually 

 mature females. With a lens the males can be readily distinguished by 

 the presence of the modified pleopods (second). During the summer some 

 females proclaim their sex by the presence of a brood-pouch containing 

 developing eggs or young Aselli. I have records of egg-laying showing- 

 considerable variation ; the earliest date on which I have captured a female 

 with eggs in the brood-pouch is January 24tb, and if the weather is fairly 

 mild they can be found in this condition as late as the end of November. 

 In the North of England from April to June is the most active period for 

 reproduction. 



Male. There are three pairs of testes lying in the middle region of the 

 thorax. Each testis is an ovoid body attached by a very short duct to the 

 vas deferens of its side. The two vasa deferentia, fairly thick tubes, extend 

 from about the 3rd or 4th segment to the 7th. Each opens separately by a 

 spout-like aperture, which, protruding from the last thoracic segment, lies 

 Justin front of the small rudimentary first pleopods (PI. 25. fig. 6). They will 

 discharge in the immediate vicinity of the second pair of pleopods. These 

 appendages (PI. 25. tig. 7) are modified for the purpose of passing the mass of 

 spermatozoa to the female. The struct lire can be seen from the figure. It is 

 the endopodite which is specially modified, forming something of a tube. 

 The general shape is triangular, and its attachment to the protopodite allows 

 great freedom of movement. The distal end is knob-like, with a pointed 

 recurved process not far from the end. 



