Mr. A. Tulk on the Anatomy of Phalangium Opilio. 319 



above by tbe medio- and lateral abdominal nerves. It consists of 

 two chambers of considerable size and conical in form^ with their 

 apices directed forwards, which communicate by a constricted por- 

 tion (*) with each other, this last being, in the natural relation of 

 parts, covered from below by the sheath of the ovipositor as it lies 

 along the median line. The right chamber, somewhat the largest, 

 opens by its small extremity into the ovarium, marking where 

 that organ returns into itself, while the left gives origin to the 

 oviduct. In an un distended state they occupy but a comparatively 

 small space in the abdominal cavity, but when filled with ova 

 (PI. V. fig. 27.) their size is so much increased, as, along with the 

 ovipositor and its retractor muscles, to be almost the only parts 

 seen upon removing the ventral integument. It is in these cham- 

 bers that the ova in all probability acquire their final coverings 

 and development previous to being laid. 



The oviduct (PI. V. fig. 26. ov), broad at its commencement, 

 appears like a continuation of the left chamber, from which it 

 curves backwards, and makes several folds as a long narrow tube 

 lying beneath the ovisac. Its direction is then forwards, to enter 

 the base of the ovipositor, and it crosses in one part of its course 

 the left retractor muscle of that organ. Its length is about twice 

 that of the ovipositor, and its texture, as well as that of the an- 

 terior part of the ovarium, must be very extensible, to admit of 

 the passage of ova through such narrow and seemingly dispro- 

 portionate canals. 



The ovipositor is an elongated, flattened and carinate organ 

 (PI. V. fig. 28.), grooved upon its upper aspect, which lies, in- 

 cluded within its sheath, along the median surface of the abdomen 

 immediately beneath the integument, through which it is visible 

 externally as a dark line ; a character by which, independently of 

 the greater size and convexity of the abdomen, the female may be 

 at once readily distinguished from the male of P. Opilio. It is 

 lodged partly within the concavity of the sternal plate, near to the 

 free border of which it terminates, and its length is about half or 

 two-thirds that of the abdomen. Above, it is in relation with the 

 anterior part of the ovarium, the constricted portion of the ovisac, 

 and the oviduct, and on the sides with the branches of the medio- 

 abdominal nerve and the lateral margins of the sternal plate. It is 

 composed of a series of horny rings (PI. V. fig. 28. a), thirty-three 

 in number, which increase in transverse width from the posterior 

 extremity to about the middle of the organ, whence they diminish 

 again towards its apex. They are furnished each with a single row 

 of bristles having elevated bases, and two of which project hori- 

 zontally outwards from the seven or eight anterior annuli beyond 

 either side of the ovipositor, diminishing however in length and 

 number behind these segments. The first and one or two last 



