THE STOMATOPODA 325 



which supply the rostrum and the dorsal " Zoea "-spine of the larval 

 carapace. 



The blood from the respiratory appendages of the pleopods 

 passes to the pericardium by a series of afferent canals in the 

 abdomen. 



E.i'cretory System. It is stated by Kowalevsky that the maxillary 

 gland is well developed in the Stomatopoda, but no details as to its 

 structure appear to have been published. A papilla on the posterior 

 surface of the maxilla in Squilla mantis (Fig. 189, C, o) bears a 

 minute terminal pore which may be the aperture of the duct of 

 this gland. 



Nervous System. The oesophageal connectives are elongated, 

 and a postoral antennal commissure is present. The first eight 

 pairs of ganglia in the ventral chain are coalesced, but the remain- 

 ing nine are widely separated. 



Sense-Organs. The paired eyes are always set on movable 

 peduncles and vary greatly in size in the different species. The 

 nauplius-eye, often present in the larvae, does not appear to have 

 been found in the adult. Sensory filaments are developed on the 

 outer branch of the external flagellum of the antennules. 



Reproductive System. The testes lie in the abdomen and have 

 the form of fine convoluted tubes uniting posteriorly in an unpaired 

 piece which lies in the telson and passing anteriorly into the vasa 

 deferentia. Each vas deferens opens to the exterior at the end of 

 a long penis springing from the inner side of the proximal segment 

 of the last thoracic appendage, and differing from the corresponding 

 organs of other Malacostraca not only in its great length but also in 

 the fact that it is more or less strongly chitinised and is divided by 

 a movable articulation about the middle of its length. In the 

 posterior thoracic somites lie a pair of convoluted tubular glands 

 which in their form and disposition have a remarkable similarity to 

 the testes, being united anteriorly by a short unpaired piece and 

 continued posteriorly into ducts which traverse the penes along- 

 side of the vasa deferentia and open beside them at the tip. These 

 glands and their ducts never contain spermatozoa and their function 

 is unknown. The spermatozoa are spherical in form, without pro- 

 cesses of any kind, and appear to be simple nucleated cells. 



The ovaries are, in the mature female, very voluminous and 

 closely approximated, so that they appear to form a single-lobed 

 mass which extends through the abdomen and as far forward as the 

 hinder limit of the carapace. In reality the two ovaries are only 

 united, as is the case with the testes, by an unpaired portion lying 

 in the telson. The oviducts open near the middle line on the 

 sternal surface of the sixth thoracic somite, together with a small 

 pocket-like invagination of the integument which functions as a 

 receptaculum seminis. On the ventral surface of each of the three 



