New Cladocera of the English Lakes. By Conrad BecJc. 779 



The digestiYe system is simple. Folding over the opening of 

 the oesophagus is a large upper lip or labrum, and below is a 

 minute lower lip or labium. Underneath the labrum the two 

 mandibles meet, and below these is a pair of small maxillae ; these 

 constitute the organs of the mouth from which the oesophagus, a 

 muscular tube, conveys the food to the stomach. The stomach 

 has no caeca, but is laterally dilated anteriorly; it extends the 

 complete length of the body, and terminates in the anus between 

 the terminal spines of the abdomen. The ovaries lie one on 

 either side of the digestive tract. The heart, which is situated at 

 the back of the animal above the brood-chamber, is large, and of 

 a triangular form ; the venous openings are in the centre, one on 

 each side, in the form of long sHts. 



Apipendages. — The first pair of antennae (fig. 2) are situated 

 on the ventral surface of the head. They are short cylindrical 

 bodies fixed immovably to the shell, and provided with a few setae 

 at their extremities, ahke in both sexes. The second antennae 

 are unlike those of any other Cladocera, in which a basal joint 

 articulates on the shell, and carries two branches at its end. But 

 in Holopedium the large basal joint is fixed firmly to the shell, 

 though it is so flexible as to make up for the loss of the joint, 

 which would be of little use within the jelly. At its end there 

 is only one branch, consisting of two segments, the last of which 

 carries three long apical setae beset with fine hairs on each side. 

 This pair of appendages protrudes through the jelly, is the sole 

 organ of locomotion, and by its slow wavy strokes produces a 

 gradual upward motion. In the male it is biramous and pre- 

 hensile. 



The mandibles (fig. 3) and maxillae (fig. 4) do not require 

 special notice, being essentially the same as those of the Sididae. 



The six pairs of feet (figs. 5-10) are similar to those of the 

 Sididae, but are longer in comparison ; they are kept in constant 

 motion, and thus serve both to respirate the blood and to bring 

 food to the mouth. In the male the first pair is prehensile, and 

 carries a hook at its end. 



The post-abdomen is short and conical, being nearly in a 

 straight line with the body and not bent up as is the case in 

 the Daphniadffi ; it is thus entirely uncovered by the shell. It 

 is beset with two rows of spines on each side, and each of the 

 terminal spines carries a smaller one at its base. The abdominal 

 setae are situated at the end of a cylindrical lobe, which projects 

 some distance from the hinder part of the abdomen. 



Hellich states that wherever he found Solopedium he also 

 found Conochilus Volvox, and I may add that in the waters where 

 I found Holopedium abundant, I also found swarms of grouped 



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