38 HOUGHTON^ ON THE GLOSSIPHONID^. 



down the maiu dorsal vessel, instead of up it. I feel 

 confident, however, that they have such . a function as I 

 have endeavoured to explain. 



Respiration in the Glossiphonidse is, no doubt, in some 

 measure carried on by the entire skin, as in the true red- 

 blooded leeches, the vital fluid being oxygenated by fresh 

 currents of water, which the animal is careful to create by 

 attaching itself by the two extremities, and waving in an 

 undulatory manner the intermediate portion of its body. 

 There is, however, another and a very important method 

 by means of which the respiration is performed. All 

 the members of this groiip have the margins of the body 

 much dilated and very thin. Careful focussing of the micro- 

 scope will enable the observer to recognise the presence of 

 minute channels doAvn each side, which lead from the two 

 main lateral vessels to the extreme verge of the margin; 

 into these channels the blood flows, describing a kind of a 

 circuit, and returning again to the lateral vessels; the 

 extreme tenuity of the margins must thus allow the blood to 

 be freely and rapidly renewed in those vessels which per- 

 meate it by the contact of the water which surrounds the 

 vessels, and which is thus brought into close proximity with 

 them. 



The nervous system in these animals is readily recognis- 

 able by dissection ; it lies on the ventral surface, and consists 

 of a nervous cord, or, as it is usual to say, of two nervous 

 filaments united together, having a large, ganglionic, oesopha- 

 geal ring, with about twenty ganglia situated at irregular in- 

 tervals one from the other, the last ganglion being the largest. 



The generative organs are represented in Plate III, fig. 11. 

 In the spring of the year a long, white band may be discerned 

 through the integuments of the abdomen, reaching some way 

 down towards the posterior extremity ; these are the testes, 

 which descend as lengthened filaments and then turn back again, 

 the ascending and descending lines being entwined together. 

 The spermatozoa are arranged in curious, curved, wedge- 

 shaped masses, and, at the proper season, an immense quan- 

 tity of these may be seen. The female organ is just under- 

 neath the male. The ovaries are two sac-like, membranous 

 lobes, within which, at one period of their development, are to 

 be seen several round vitelli, which are attached on either side 

 of a long, tortuous cord ; these are, of course, detached from 

 the funiculus before exclusion. Notwithstanding most 

 attentive observation, I have never witnessed anything like 

 a generative act in any of the numerous indinduals which I 

 have had under inspection. F. Miiller, however, has proved 



