EYES OF THE SEROLIDiE 359 



water by the character of the eyes. ' The results,' he says, 

 ' of my investigations into the minute structure of the eye 

 in Serolis may be briefly summed up as follows : — (1) The 

 shallow-water species invariably possess well-developed 

 eyes which are fundamentally similar to those of other 

 Isopoda, but differ in several particulars ; the retinulse are 

 composed of only four cells ; the rhabdom is often a highly 

 complicated structure unlike that of other Crustacea. 

 Another element unrepresented (?) in the eyes of other 

 Crustacea is present, consisting of two large hyaline nu- 

 cleated cells placed below the rhabdom and between the 

 retinal cells. (2) In the deep-sea species the eyes are 

 either altogether absent (Serolis antarctica), or, if present, 

 show signs of structural degeneration; no retinula, at 

 least nothing comparable to the retinula in the eyes of the 

 shallow-water species, is present, but the vitreous body is 

 represented. The vitreous bodies may be enclosed in a 

 sheath of pigment (Serolis necera), or there may be no 

 pigment present (Serolis gracilis, Serolis Bromley ana).' 



Prom examination of the contents of the stomachs 

 Mr. Beddard has come to the conclusion that these inter- 

 esting Crustaceans are upon occasion cannibals. 



Family 5. — Sjplueromidai. 



The body is convex, the head transverse ; the pleon is 

 vaulted over the pleopods, its earlier segments, exclusive 

 or inclusive of the first, being usually fused into a shorb 

 segment marked more or less by sutural lines, the terminal 

 segment being, on the other hand, very large. The eyes 

 are generally wide apart ; both pairs of antennae have the 

 flagellum multiarticulate and well marked off from the 

 peduncle. The mandibles have a three-jointed ' palp ; ' 

 the first maxillse have two plates, the second three ; the 

 maxillipeds are seven-jointed, the second joint being pro- 

 duced into a plate. The limbs of the peraeon are slender, 

 generally with bifid fingers. The first three pairs of pleo- 

 pods are ciliated, with the outer branches not opercular ; 

 the second pair in the male have a stilet on the inner 



