92 



BRANCH ARTHROPODA 



The barnacles (Lepas) are found in clusters on the bottom of 

 ships and often greatly impede their progress. 



Fig. 66. — Anatomy of Lepas fascicularis (Packard): A, c, Six pairs of 

 legs or cirri; /, filamentary appendages; m, mouth; s, stomach; h, openings 

 of the liver (1) into the stomach, which is represented as laid open; i, in- 

 testine; n, vent; t, testis; v, vasa deferentia, one cut off; p, male appendage; 

 0, ovary; e, adductor muscle connecting the two basal valves; rs, scutal 

 valve; re, carinal valve; vt, tergal valve. Enlarged twice. B, 1, Palpus; 

 2, mandibles; 13 and 4, first and second maxillte. C, Nervous system: s, 

 Brain, sending the optic nerves to the rudimentary eye (< ), each optic 

 nerve having an enlargement near the eye, i. < ,, the ojihthalmic ganglion 

 (o): between o and a arc the nerves which go to the peduncle; a. nerve 

 sent to the adductor scutorum; ce, commissure between the supra- and 

 infra-esophageal ganglia (n); c, c, c, c, c, c, nerves to each of the six feet. 

 Enlarged four times. (After Kingsley.) 



Sub-class II. Mal'ac6s'traca is composed of crustaceans of a 

 definite number of segments, usually twenty — the head of five 

 segments; the thorax, eight; and the abdomen, seven. These 



