ZOOLOGY. 313 



cerned. The quickness with which these animals kill others which 

 come in their vicinity, leaves no doubt that these little microscopic 

 cells, with these threads, are most powerful weapons, by which they 

 attack and kill their prey almost instantly. 



"How does this thread, which is so long-, uncoil and come out from 

 the cavity of the cell? It is as quick as lightning 1 , and therefore the 

 more difficult to observe, as the whole thread, which is twelve OF six- 

 teen times longer than the longitudinal diameter of the original cell, 

 is thrown out in almost an instant. It is here that I reach the ex- 

 treme limits of the working power of our microscopes. In observing 

 the cells, three times in succession, I saw the thread thrust out, at 

 first appearing to turn with great rapidity upon itself within, and 

 then, after a part had been pressed out, the extremity of the thread 

 within came in sight and could be traced as it escaped through the 

 whole length of the part already drawn out, until the whole was ex- 

 tended and the point actually projected outwards ; so that this fine 

 thread is in fact a tube, and is finally turned inside out to the very 

 extremity of the thread. Now, conceive what extraordinary struc- 

 ture this apparatus must have to allow of such a motion ! Our 

 micro:-copes now do not reach at all the limits which they should 

 reach in order to enable us to trace the structure by which such phe- 

 nomena are produced. I only describe appearances now; but it is 

 evident that an apparatus subservient to such a purpose, and acting 

 with such rapidity, cannot but be highly complicated in its structure, 

 although that structure is so minute as to escape the eye, even when 

 armed with most powerful magnifying apparatus. 



"Having described the peculiar form of the nettling cells of this 

 coral-building animal, let me say what I have further seen about it. 

 The festooned head of a tentacle, which is hemispherical, may send 

 out from its termination thousands of these lassos at once, so that the 

 summit of the tentacle is then like a formidable wall of peaks stand- 

 ing out in all directions, and between them all are vibrating cells with 

 their myriads of cilia maintaining currents of water, the threads 

 standing out from the empty capsules. It is impossible to give a 

 description vivid enough to convey the idea of such an apparatus as 

 this presents when sent forth against its prey. But it can readily be 

 imagined how formidable such a contrivance must be, when these 

 animals can reach out so far beyond their apparent surface and stretch 

 forth these unseen organs of apprehension. These animals are, it 

 will be perceived, most dangerous enemies to the small living beings 

 around them, since the radius of their reach is so far beyond their appa- 

 rent surface, owing to the length of their lassos." 



THE SEA-COW. 



AT a late meeting of the Boston Natural History Society, the 

 President, Dr. John C. Warren, introduced a subject of particular in- 

 terest to those who have paid any attention to the study of the ani- 

 mals which are found on the shores of the United States. 



It has long been known, that a large marine animal occurs about 



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