A NEW SPECIES OF PENTASTOMUM. 181 



equal length and breadth (0*28 mm.), while its thickness amounts to about 

 014 mm. A general view of its form and position, with the branches given 

 out from it, is given in the dissection depicted in PI. XXVIII. fig. 16, n.g. 

 The two larger branches, which pass backwards, can be traced for more than 

 half the length of the animal ; they lie in the main parallel to each other, one 

 on either side of the ventral median line. From either side of the large ganglion 

 a branch passes along the oesophagus, and probably reaches the oral papilla. 



In connection with the structure described by Lienard * in several other 

 Arthropods (Spirocyclistus, Cossus), it is interesting to note that the praeoeso- 

 phageal commissure in my specimens was double, and from the anterior cord 

 two branches proceeded forwards. 



The minute structure of the nervous system was so ill-preserved that no 

 observations of value could be made upon it. 



The Generative Organs. 



Both male and female specimens were fortunately present among those I 

 had for examination, but while the genital apparatus of the former presented 

 some noteworthy arrangements, that of the latter was not specially remarkable. 



The Male Organs. 

 These may conveniently be described under the following heads : — 



1. The Testis. 



2. The Vesicula seminalis. 



3. The Vas deferens. 



4. The Cirrus Sac. 



1. The Testis (PI. XXVII. fig. 5 ; PI. XXVIII. figs. 1-6, /) is situated on the 

 dorsal surface of the intestine ; it is an unpaired, long, very thin walled sac, 

 extending from a point some 4-5 mm. behind the head, to within about 1 mm. 

 of the posterior extremity, where it ends in a mass of small parenchymatous 

 cells, which lie on the dorsal aspect of the intestine. Its greatest breadth 

 (measured from side to side) is 0*7 mm., whilst its thickness (dorso-ventral) 

 will be rather more than one-third of this. 



The wall of this gland consists of a thin, and to all appearance, structureless 

 membrane, which becomes very deeply stained by hematoxylin, and measures 

 0004 mm. in thickness. It is attached to the dorsal wall of the body-cavity 

 by a thin cellular mesentery (PI. XXVIII. fig. 3, m.e) which is precisely similar 

 in structure to those supporting the intestine, already described. 



In the immature specimens under consideration, the gland contained only 



* Lienard, "Constitution de l'anneau cesophagien," Arclriv. d. Biol.,%. i. p. 381, 1880. 

 VOL. XXXII. PART J. 2 G 



