SAPPHIRINE COPEPODS. 123 



about equal size, and armed with strong oar-like bristles of great 

 service in swimming, Sometimes, however, as in S. Danvinii 

 (Haeckel), the inner branch is atrophied, indicating weaker swimming 



powers. 

 No gills are present; the cuticle is so thin and delicate that the 



whole surface of the body functions in breathing. 



When seen swimming the Sapphirinids present a magnificent play 

 of metallic colours the acme of iridescence as they drive rapidly 

 through the water, mere sapphirine glints of darting light ; the reason 

 for the generic name is obvious. If we examine the cuticle, the cause 

 of the ever-changing sheen is found to be due to excessively fine 

 parallel and cross rulings upon the surface that produce the optical 

 effect of lightning-swift colour change with every alteration in the 

 incidence of the light. 



The cuticle is underlaid and produced by an excessively thin layer, 

 the hypodermis, in which lie numbers of most peculiar dermal glands. 

 Their proportion varies greatly in different species, attaining greatest 

 development in S. Edwardsii (Fig. I.), where they are thickly scattered 

 over the whole body. Each opens to the exterior by a fine duct 

 passing through the cuticle. Usually they are unicellular as in the 

 species named ; more rarely they are multicellular, as in S. Danvinii, 

 composed of from three to seven or even more cells. Usually each 

 gland is accompanied by a nerve ganglion giving off a sensory bristle 

 or seta that projects from the surface of the cuticle. A common nerve 

 serves each pair, breaking into two branches ere reaching them. The 

 function of the glands is excretory ; its activity is apparently 

 controlled from its companion nerve cell, which in turn receives im- 

 pressions from the surrounding medium through its projecting seta 

 (see Figs. II. and V., y., pg. and yg.). 



A former article in Vol. I., p. 42, described the muscular arrange- 

 ment of Honstrilla, an allied Copepod. That of Sapphirina is on the 

 same plan. 



The oesophagus passes through the centre of the ganglionic mass, 

 and leads directly into a dilated stomach provided with glandular 

 diverticula or pouches that may be considered as acting the parts of 

 liver and pancreas (L). The form of this " liver " varies with the species ; 

 note how in S. Edwardsii it forms a collar-like mass around the anterior 

 end of the stomach, while in S. Gegenbauri it forms four pouch-like 

 branches. The intestine is straight, ending between the caudal plates. 



The Nervous System exhibits great centralization. There is no 

 distinction into brain and ventral ganglionic chain such as is seen in 

 the free-swimming Copepods. All are fused into one great ganglionic 

 mass pierced by the oesophagus. But as a compensation, or indeed as 



