832 Transactions of the Society. 



dark-coloured organs, fastened by one end to the inside of the wall 

 of the abdomen, close to the junction of the first and second 

 somites. The inner ends are free, the right-hand ovary projecting 

 into the abdomen downwards; the left upwards. When much 

 distended with eggs they sometimes nearly fill the abdomen. My 

 friend Mr. W. P. Marshall informs me that he saw one female 

 with a row of eggs the whole length of the abdomen, but I did not 

 see the specimen myself. The oviducts open on to the surface 

 between the second and third somites. The eggs, after extrusion, 

 are carried about in the carapace of the mother until hatched. 

 The way in which they are kept in their places is very remarkable. 

 The carapace (omostegite) is much larger in the female than in 

 the male (Fig. 5, female, and 1, m, male), shaped like the bowl of a 

 spoon, with the edges produced and curled over inwards. It is 

 this incurvature of the edges which prevents the eggs from 

 tumbling out of the carapace, as shown in Fig. 6, which is an ideal 

 section of the carapace and abdomen showing two eggs, and the 

 way in which the opening is closed below by the top of the 

 abdomen. The eggs are always arranged round the carapace, 

 never in the middle, and the greatest number I have seen within it 

 at one time is six. I am indebted to Mr. J. Levick for a specimen 

 showing the structure of the female carapace very clearly. 



Tlie testes (Fig. 2, ?/) occupy the same position in the male as 

 the ovaries of the female. They each consist of an elongated, 

 transparent sac, pointed above and below, and connected together 

 by a saddle-like band. They are filled with sperm vesicles, most 

 thickly congregated towards the upper end. As my paper only 

 treats of the anatomy of the animal, I cannot enter into the subject 

 of its development, although it is highly interesting. 



VI. Zoological Position. 



Le^toclora hyalina was placed by Lilljeborg in the Branchio- 

 poda. Order Cladocera, and Family Daphniadas, and his placing 

 has since been admitted by other naturalists without demur ; but, 

 during the last two months. I have had the animal under close 

 observation, and the more I study it the more the conviction grows 

 upon me, that its departure from the type is so great that one of 

 two things must happen. Either the diagnosis of Cladocera and 

 Daphniadee must be altered in order to admit the species, or else 

 Leiitodora must be placed in a separate order and family. The 

 following is Baird's description of the order Cladocera, condensed. 



Body, except the head, enclosed in a bivalve carapace hinged at 

 back. Feet four to six pair, articulations chiefly branchiform, not 

 adapted for locomotion. Eye single, large. Antennae two ])airs, 

 inferior branched, large, and adapted for swimming. Mandibles 

 without palpi. 



