1922. No. 5. ARIOXIDAE OF NORWAY. 23 



the last days of June, and I never had an opportunity of studying the 

 entire process. 



It reaches maturity at the age of 8^ 2 — lo months. Before copulation, 

 which may be repeated several times by the same animal, a prelude of 

 I o to 90 minutes takes place, during which the animals crawl round each 

 other and lick the mucus from the caudal cavity of each other. Then the 

 movement ceases, the reproductive organs are opposed and the genital 

 atrium of each is turned inside out; this voluminous body being pressed 

 to that of the partner, the ligulas are fixed to each other, undoubtedly acting 

 like suckers. Both animals are immovable, the tentacles are withdrawn, 

 and then the epiphallus of each is put into the stalk of the receptaculum 

 in the other, while the spermatophore is transferred. The actual act of 

 copulation may last for more than two hours. When the animals separate 

 the long tail of the spermatophore projects from the opening to the recep- 

 taculum, but dissappears when the atrium is drawn in. 



As to the fertilization the statements of KCnkel I1916) cited above 

 (p. Ill are not in accordance with those of Lams (1910I. The latter proves 

 that in Arioii atcr the fertilization is "intra-ovarial", and further that the 

 spermatozoa do not lose their tails in the receptaculum, as the remnants 

 of the tail may be seen within the fertilized ^^^. — KCnkel (1916) showed 

 that Arioii atcr may multiply by self-fertilization through five generations. 



The deposition of the eggs, too, has been carefully studied b}^ KCnkel 

 (191 6), according to whom it takes place for about two months, during 

 which period ma}- be deposited as many as 500 eggs. They are not deposited 

 continuously, howewer, but in 3 — 8 hatches, each containing from about 20 

 to about 250 eggs. As Wotton mentions (1893) each laying lasts up to 

 40 hours, and all that time the animal does not stir, the head being drawn 

 in under the shield; the laying goes on even if the animal is placed on 

 the hand of the observer. 



The eggs are laid in a sheltered place, such as in loose earth, under 

 leaves or moss, where they run no risk of becoming dr}'. When deposited 

 they are white and semi-transparent, but later on they grow yellow and 

 opaque. The size and form var}' very much. Usually they are oval, 

 4x5 mill., but the diameter varies from 3 to 8 mill., and they not rarely 

 have the shape of globes of equal size. 



The embryonic development is of unequal duration, even in the same 

 hatch. According to KCnkel it varies, in accordance with the temperature, 

 from one to four months. 



When leaving the egg the young ones are about i cm. long. In Nor- 

 way they are usually pale with yellow spots, but they are even said to 

 have a quite pale yellow, reddish or a pale grenish colour appearance. 



Under favourable conditions they grow up quickly. In the common 

 black variety the dark pigment slowly appears, in such a way that first 

 the tentacles, and often the head, too, become a bluish-black colour; in 



