330 EVEXES'GS AT THE MICROSCOPE. 



wide cavitj apparently quite emptv, as the blue cal- 

 careous stem extends only half-way from the base to the 

 head. At tliis point the neck contracts rather abruptly, 

 and continues to the base, but just wide enough to in- 

 vest the stem. 



This sort is confined, so far as I have seen, to the 

 ovarian plates and their vicinity, where they are nu- 

 merous. 



Thus these tiny organs, so totally unlike anything 

 with which we may parallel them in other classes of 

 animals, do not merely afford us amusement, and de- 

 light us by their elegance of shape and sparkling 

 beauty, the variety and singularity of their forms, the 

 elaborateness of their structure and the prefection of 

 their mechanism, but excite our marvel as to what caj 

 be the object which they subserve in the economy of the 

 creature — what purpose can be fulfilled by so many 

 hundreds of organs so singular, and scattered over the 

 whole surface of the shelly body. 



It is very diflicult to answer this question. The 

 only organs with which they can be compared are the 

 singular " birds' heads" in so many of the Polysoa, 

 which we looked at some time ago. But, unfortu- 

 nately, a like mystery enshrouds the use of those pro- 

 cesses, and the only light that we have as yet upon 

 either form is that of dim conjecture. It has been sup- 

 posed that, in both cases, the function of the prehensile 

 forceps is to seize minute animalc;ules or floating atoma 

 of food, and pass them to the mouth : but the supposi- 

 tion is involved in great difliculties ; as the organs, 

 liowever fitted for prehension, seem peculiarly unsuited 

 for transmitting objects ; besides that the great majority 

 of them are placed very remote from the mouth. I can 



