Structiwe of an Aastrclldi} Lavd Lecclt. 219 



between tlie integument in the neiglibourhood of the genital 

 organs and that of the rest of the body. 



As already stated, the male and female reproductive organs 

 open on the 26th and 30th annuli respectively, that is the second 

 annul us of somites X. and XT., so that they occupy a similar 

 position in their respective segments — namely mid-ventral on the 

 posterior border of the second annulus. The median region 

 includes the greater part of the body made up of unabbreviated 

 somites though externally there is nothing which can determine 

 the position or number of annuli in a segment, that is, no clearly 

 distinguishable segmental papillie and no visible nephridiopores. 

 Each segment in this region possesses a ganglion, from which are 

 given off nerves to the diftierent parts of the segment as well as 

 the portion of the ventral chain connecting the ganglia, a pair of 

 nephridia, each with its excretory vesicle and external aperture, 

 a pair of testes and a portion of the alimentary canal with a 

 ■diverticulum given off on each side. 



The hindermost end, including the anal and acetabular regions, 

 Again shows centripetal abbreviation (Figs. 1, 2, 3). 



Behind the last annulus, 79th in the mid-dorsal line, is situated 

 the anus on a small muscular papilla attached to the acetabulum. 



Integuinent and Sense Organs. 



The integument of this form resembles very closely that of 

 other described land leeches. It consists on the outside of a thin 

 transparent cuticle, beneath which lies the epidermis made up 

 of columnar cells and simple unicellular glands, in many of 

 which the nucleus can be clearly distinguished lying at the side, 

 as shown by Bourne. Distributed among these cells are numerous 

 capillaries supplied from the dorsal and ventral sinuses, and 

 joining together to form vessels pouring terated blood into the 

 lateral vessels. Here also the pigment is disposed. In certain 

 parts the epidermic cells are modified and specialised to form 

 sense organs. Of these there are the segmental sense organs, the 

 eyes, and the marginal lip organs — or "goblet-shaped" organs of 

 Leydig. 



In the main the sense organs of Philjemon resemble those of 

 the leeches worked at by Whitman. 



