THE OSTRACODA 59 



the antennules are modified in the male sex as organs for clasping 

 the female. This appears to be the function of certain highly 

 peculiar setae provided with sucker-like organs found in the male 

 of Cypridina. 



With very few exceptions the antenna appears to be the chief 

 organ of locomotion, whether swimming or creeping. In the 

 Myodocopa it is biramous, and the outer branch is more strongly 

 developed than the inner, with eight or nine segments carrying 

 natatory setae. The inner branch has not more than three 

 segments, and is often modified as a clasping organ in the male. 

 It is characteristic of the Myodocopa that the single segment of 

 the peduncle is greatly expanded and occupied by large muscles 

 (Fig. 34, B). In Polycope (Cladocopa) the two rami do not differ 

 greatly in length. In the Podocopa only one ramus of three or 

 four segments is well developed, and, according to the view of 

 G. W. Miiller, it is the inner ramus, the outer being represented 

 by a small process tipped with setae or being altogether absent 

 (Fig. 34, D). In Cytherella (Platycopa) the antenna differs from 

 that of all other Ostracoda in having the peduncle divided into 

 two segments and bent or geniculate between them (Fig. 34, C). 

 The two rami are well developed the inner, of three segments, 

 resembling that of the Podocopa in the disposition of the sensory 

 setae. The outer ramus has two segments. In the Cytheridae a 

 large seta, bent at the tip, occupies the place of the vestigial outer 

 ramus present in the other families of Podocopa. It serves as 

 duct to a large unicellular gland. This was formerly regarded as 

 a poison-apparatus, but, according to Miiller, it is a spinning organ, 

 by means of which the Ostracod covers with a network of fine 

 threads the surface on which it is creeping, in order to obtain a 

 secure foothold. 



The labrum is usually well developed, and is especially large in 

 Cypridinidae, where it contains a group of gland-cells. The lower 

 lip is usually small, and only rarely shows traces of a division into 

 paragnatha. 



The mandible is characterised by the large size of the palp, 

 which is often biramous and is sometimes pediform or variously 

 modified. The gnathobase may be reduced to a small setose lobe 

 (Cypridina), or to a curved serrated process extending into the gullet 

 (Asterope). In Sarsiella it seems to be entirely absent, and the 

 strong curved spines with which the tip of the palp is armed 

 probably serve for seizing food and passing it into the mouth 

 (Fig. 35, C). In the other families the gnathobase is usually well 

 developed, and armed with spines and teeth. The palp usually 

 consists of four segments, but the number is often reduced. In 

 the Cypridinidae it is long and pediform, and is used in creeping. 

 In Sarsiella, as already noted, it serves for the prehension of food, 



