250 Mr. A. Tulk on the Anatomy of Phalangiuin Opilio. 



transverse outlet upon the under surface of the abdomen, he would 

 hardly be prepared to find, in dissecting one of the present group 

 of animals for the first time, not only well-developed internal 

 organs, but an external male and female apparatus for repro- 

 duction, comparable even, from its size and complexity, to that 

 met with in insects. To such a degree may important differences 

 in the structure of internal parts be masked by analogies of out- 

 ward form. 



The organs of generation in the male of Phalangium Opilio 

 consist of a penis inclosed within a sheath, a vas deferens, and 

 certain excretory glands, the analogues of the testes. All these 

 parts are situated within the cavity of the abdomen towards its 

 anterior extremity, lying along its under surface, immediately be- 

 neath the integument. 



The testes are formed by a cluster of elongated, narrow and 

 slightly tortuous cffical tubes (PI. IV. fig. 21. st), situated above 

 the sheath of the penis when the latter is " in situ," and which, 

 converging towards a central point, combine to form a single sper- 

 matic duct (r), which is continued onwards to the extremity of 

 the male organ. The above cluster of seminal tubes is in relation 

 above with the medio-abdominal nerve, which crosses over it, and 

 the under surface of the gastric sac ; on either side of it are seen 

 the long inferior cseca of the latter, and emerging from among 

 the lateral tubes, the nervous ganglia {iig') which supply these 

 organs. 



The duct or vas deferens [v), given off as already stated, passes 

 in a tortuous direction above the testes, which it resembles in tex- 

 ture very much in the posterior half of its com'se, and extends to 

 about twice their length within the abdominal cavity. Its ante- 

 rior half is tough and horny (v"), and surrounded, nearly as far 

 as its entrance into the penis, by an oblong ovoid body of consi- 

 derable density and thickness [v). 



Th.Q penis (PI. IV. fig. 22. jw), though simple in its structure, 

 is remarkable from its length, nearly equalling the half of that 

 of the abdomen. It is composed of two distinct portions, a body 

 {p) and glans {y), both of a very firm coriaceous texture. 



The body, which constitutes by far the largest portion of the 

 organ, is shghtly cm'ved throughout its entire length, the conca- 

 vity being directed upwards, and broad behind at its commence- 

 ment, gradually narrows towards its anterior extremity. It is 

 compressed from above downwards and grooved upon the upj^er 

 surface. At its base it presents superiorly a large crescentic 

 opening (o) for the passage of the continuation of the spermatic 

 duct, or the ductus ejaculatorius, which traverses it throughout 

 as a rigid horny tube [t), and opens into the base of the glans. 

 The termination of the body of the penis in front is somewhat 



