PROTRACHEATA. 531 



a double row of stigmatic apertures on either side the median dorsal line, 

 and similar rows on either side the median ventral line ; other apertures are 

 found on the anterior and posterior aspects of the feet, at their base, on 

 the dorsal aspect of the head, and a single large median ventral aperture 

 in front of the mouth. Each stigma leads into a pit dilated internally, 

 from which proceed bundles of unbranched extremely minute tracheal 

 tubes, lined by a cuticle which has a faint transverse striation. They are 

 distributed to the muscles, viscera, nervous system, &c. A nephridium 

 opens ventrally near the base of each foot. It consists of a vesicle opening 

 externally ; a coiled tubular portion ; and a terminal funnel (? ciliated) which 

 opens into the section of the coelome in the foot, from which it is stated 

 to be differentiated (cp. the Elasmobranch excretory system). The three 

 first pairs of nephridia are rudimentary, the fourth and fifth enlarged and 

 somewhat peculiar. The sexes are separate. The male has a pair of 

 testes, each with a prostatic gland. The two vasa deferentia unite, and 

 then receive terminally the ducts of a pair ef tubular accessory glands. 

 The ovary is single, but divided by a longitudinal vertical septum into 

 two halves. The two oviducts dilate into uteri in which the embryo 

 is developed. They unite in a terminal vestibule. The generative aperture 

 is ventral and in front of the anus. The filiform spermatozoa are united 

 into rodlike spermatophores, which the male attaches to the body of the 

 female in any region. Segmentation is complete. The blastopore in P. 

 capensis is elongated and divides, forming both mouth and anus. The 

 young differ at birth from the adult only in size and colour. 



P. Edwardsi differs in some respects from P. capensis. Crural glands 

 are absent in the female, present in the male only on the 7-8 pairs of 

 prae-genital limbs. Bean-shaped vesicles to which muscles are attached 

 and nerves distributed are lodged on the dorsal aspect near the claw of 

 each limb. A pair of glands open ventrally in the male, one on either side 

 of the anus (? = accessory male organs of P. capensis). The stigmata are 

 irregularly scattered. There are no anal papillae. The sexual aperture 

 lies in the penultimate somite between the last pair of limbs. The 

 prostate gland of Moseley is the real testis and gives origin to the 

 spermatospores, which undergo development in the dilated portion or 

 testis of Moseley. The united portion of the vasa deferentia is divisible 

 into three regions, an anterior in which the sperm collects, a middle in 

 which the spermatophore is formed, and a terminal, the muscular ductus 

 ejaculatorius. The spermatophore is about \\ inch ( = 4 cm.) long, has 

 several envelopes, and contains the agglutinated spermatozoa in 3-5 dila- 

 tations. The female organs consist of two ovaries, each connected by a 

 ligament to the pericardial septum; of two oviducts, which communicate 

 anteriorly and have each a funnel-shaped aperture into the coelome, and 

 carry a horseshoe-shaped receptaculum semkiis communicating at each 



