620 Notices of Irish Entozoa. 



The proboscis in the microscope, especially when the worm 

 has little colour, is a very beautiful object. It is cylindrical, 

 a little thickened anteriorly, crystalline, and armed with lon- 

 gitudinal rows of solitary, transparent, sharp, rigid hooks, bent 

 backwards. These hooks alternate with those of each neigh- 

 bouring series, and hence each transverse row is not directly 

 across the proboscis, but runs obliquely, as if it were a por- 

 tion of a spiral convolution. When the worm is in the flac- 

 cid state, the proboscis is generally retracted, and of course 

 invisible ; but when the specimen is distended it is always 

 protruded, and in an oblique direction. Cloquet, in his mas- 

 terly account of the Echinorynchus Gigas* has described 

 two kinds of motion belonging to the proboscis, one by which 

 the whole organ is at the same time protruded or retracted 

 without any alteration in its form. This is effected by eight 

 muscles, four protractors which protrude it, and as many re- 

 tractors which draw it in. The second motion is of a differ- 

 ent kind, but not less necessary to the animal ; in it the pro- 

 boscis is drawn in by inversion upon itself, so that what was 

 its outer surface when extended, becomes its inner when re- 

 tracted, and vice versa, when it is again protruded the inner 

 surface becomes the outer. It is an operation similar to that 

 by which a snail draws in and pushes out its horns. 



This motion of the proboscis in the Echinorynchus Acus 

 has a very beautiful effect in the microscope, and a sure way 

 of seeing it is this. — A specimen is to be taken from the in- 

 testine, or, what is better, from the salt solution, as then it 

 will be freer from foreign matter, it is then to be placed on a 

 slip of glass, and its anterior end brought within the focus of 

 the microscope ; successive drops of fresh water are then to 

 be applied with a hair pencil. In a few moments the animal 

 shews symptoms of uneasiness, and begins to unfold and re- 

 tract the proboscis very often. The operation is generally 

 partial at first, but the instrument is soon launched out with 

 great force, and to its utmost extent, when a very evident 

 constriction or neck will be seen at its base. The power of 

 unfolding and retracting it, however, in this manner soon be- 

 comes more difficult, till at last it cannot be inverted at all, 

 and consequently, it continues fully distended ; and then it 

 may be seen protruded and drawn in alternately, but as a 

 whole, and not by a successive unfolding and drawing in of 

 its parts. The absorption of water still going on, the disten- 

 tion at length becomes so great, that the proboscis remains 



*Anatomie des Vers Intestinaux, Ascaride Lombricoide et Ecliinorhyn- 

 quc Geant. Paris, 1824. 



