STOMATOPODA. 507 



In the central nervous system the supraoesophageal ganglion is 

 a hexagonal mass (notwithstanding the apparent segmentation of 

 the front of the body) supplying nerves to the eyes and both pairs 

 of antennae. A compound ganglionic mass behind the oesophagus 

 supplies the segments from the mandibular as far as the fifth 

 thoracic, but the nine segments behind this have each their own 

 ganglion. The compound eyes have the same structure 

 as in Decapods. In Squilla the surface is not simply convex, 

 but saddle-shaped. No auditory organ has been discovered. 



In the alimentary canal the triturating stomach is only 

 slightly developed. The intestine is a slender and delicate tube, 

 1 mm. in diameter in Squilla mantis, extending to the end of the 

 fourth abdominal segment, where it joins the wider hind-gut. 

 Parallel with the gut are two longitudinal canals, which open 

 anteriorly by a common opening into the pyloric region of the 

 stomach. Voluminous caecal diverticula are given off from 

 these canals, which are segmentally disposed, in each posterior 

 segment and in the telson, and almost completely envelop the 

 intestine (Orlandi). 



The glands of which these longitudinal canals are the ducts are evidently 

 homologous with the " hepatic " digestive glands of other Crustacea. 

 Before Orlandi's researches were published the segmentally arranged 

 groups of caeca were supposed to open direct into the gut in Stomatopods 

 and thus to present a puzzling exception to the usual arrangement. 



Antennal glands are absent, but the presence of well developed 

 shell-glands has been demonstrated by Kowalewsky.* An 

 excretory function has also been suggested for a pair of rectal 

 glands. 



The heart is tubular with numerous paired ostia, and extends 

 from the fifth abdominal segment to the front of the thorax, 

 where it presents a small enlargement. Fourteen paired arteries 

 are given off from it. 



The testes are abdominal and take their origin in a slender 

 median tube. The vasa deferentia open on the tips of the 

 rod-like penes which spring from the basal segments of the last 

 thoracic legs. A pair of " accessory glands " pass backward 

 through the thorax to orifices situated close beside those of the 

 vasa deferentia. The spermatozoa are spherical, with large 

 nuclei. The males possess small processes of peculiar shape and 



* A. Kowalewsky, Ein Beitrag zur Kenntniss der Excretionsorgane 

 Biol. Centralblatt, Bd. ix (1889), p. 41. 



