Notices of Irish Entozoa. 521 



permanently extended, unless we put the specimen into the 

 salt solution for some time, and then the same phenomena 

 may be seen repeated. 



I cannot pass over this double kind of motion in the pro- 

 boscis of the Echinorynchus, without adverting to the won- 

 derful design and contrivance evinced therein. On the slight- 

 est glance, it is obvious that the object of the hooked appa- 

 ratus is to fix the animal in the intestinal coats, and thereby 

 prevent its being carried off by the peristaltic action, and the 

 mechanical pressure of the ingesta in their passage. But 

 suppose that the worm could only move the proboscis as a 

 whole, we might then indeed conceive that by simply pushing 

 it forwards against the mucous coat, there might be a chance 

 on drawing it back of fixing some of its hooks, but having 

 done so, how is it to make farther progress into the intestinal 

 walls ? The proboscis having this only motion would be very 

 inefficient, but by its more complicated economy, it is per- 

 fectly adapted to its intended ends. It is not by the point, 

 nor by the sides of the instrument, but by the circumference 

 of its base, that it first grapples with the coats of the intes- 

 tine. 



Let us suppose then that an Echinorynchus is commencing 

 the operation of fixing its proboscis in the intestinal coat ; 

 the instrument is lying inverted in its sheath, in the anterior 

 extremity of the animal, and its point is of course directed 

 backwards, as the end of the finger of a glove turned outside 

 in would be directed towards the wrist. The base, then, of 

 the proboscis thus situated, is the first part which comes in 

 contact with the mucous coat, and when the unfurling begins, 

 the hooks surrounding it are the first that are pushed into the 

 membrane, and as the eversion continues, the other and more 

 anterior hooks are successively expanded, so that those on the 

 point of the proboscis are the last which penetrate the intes- 

 tine, as those upon the base were the first. And now, I con- 

 ceive, comes the great utility of the motion of the proboscis 

 en masse, when it is now drawn back as a whole, the conse- 

 quence will be, that the hooks will be carried farther into the 

 intestinal walls, than they could be from the force applied by 

 the everting motion alone, and thus a more perfect hold will 

 be given. 



Again, we find a most perfect adaptation of the form of the 

 hooks to their office ; their shape is very different from that 

 of a fishing hook, which would not at all answer. On the 

 contrary, they are curved only at their base, the rest and lon- 

 ger part being nearly straight. By this formation they occu- 

 py very little room in the inverted state of the proboscis, and 



