36 HOUGHTON, ON THE GLOSSIPHONID^. 



different species, but the principle of mechanical action is 

 the same in all. G. bioculata, the smallest British species, 

 if put into the palm of the hand, has the habit of thrusting 

 out its proboscis to the length of, perhaps, a third of its 

 own body. I have not noticed this habit in any other 

 species. Connected and continuous with the bulbous base of 

 the proboscis is another, transparent, hollow membrane (the 

 continuation of the oesophagus), which, when the proboscis 

 is not exserted, twists and rests upon itself. At the base of 

 this membrane is the commencement of the stomach, the 

 walls of which are attached to the surface of the body of the 

 animal. The stomach is furnished with five or seven pair of 

 gastric casca, which are either simple or forked at their 

 extremities j there are also, in some species^ very small caeca, 

 in advance of the large sacs, Avhich, perhaps, have a kindred 

 function. The last pair of cseca, which is always the largest, 

 is directed downwards towards the posterior extremity, 

 while the rest are nearly at right angles to the mesial axis 

 of the body. De Filippi {' Lettera al Sign. Rusconi, sopra 

 TAnatomia e lo Sviluppo delle Clepsine,^ Pavia, 1839) 

 asserts that he has observed between the digestive canal and 

 the blood-vessels a special communication, by means of 

 which animal juices sucked by the Glossiphon pass almost 

 immediately into the blood-vessels, and that thus, by trans- 

 fusion, as it were, the snail-leech acquires a supply of blood. 

 I have never noticed anvthing of this kind in the numerous 

 examples I have submitted to patient investigation. The 

 intestine in these animals is furnished uniformly with four 

 pair of caeca, the two anterior pair of which are directed 

 upwards ; the anus, which is more readily I'ccognised when 

 the animal is out of the water, is round, and situated just 

 above the juncture of the acetabulum and trunk of the body. 

 In young specimens, and more especially in those of the 

 beautiful little species G. hijalma, the digestive caeca are 

 frequently found to be of a brilliant-red or vermilion colour. 

 Whence is this red colour derived ? Moquin Taudon 

 (^ Monographic de la Famille des Hirudinees,^ 1846) has 

 figured a young G. sexoculata [complanata) with these blood- 

 red caeca ; he says the specimen had sucked the blood of an 

 Haemopis. But if this colour be derived solely from blood 

 which the animal has swallowed, how can we account for the 

 fact that it is always, as far as I remember, in the young 

 individuals that the red colour is observed? Full-grown 

 specimens do not exhibit this appearance. I have reared 

 individuals from ova which had been deposited in vessels in 

 which it was impossible for the young ones to have obtained 



