335 



found swarming in the intestine, and evidently in such numbers 

 as to affect the life of the animal in which they reside. 



When seen in their earliest condition they consist of delicate, 

 nucleated cells of about 3-^^^ of an inch in diameter. These 

 cells cannot be regarded as ova, but rather as cast-off panicles 

 from higher organisms, perhaps separated by some scissian- 

 process. A little farther advanced they appear larger and are 

 covered with very delicate cilia on two opposite poles ; at the same 

 time the pole about which the cilia are most abundant, becomes 

 a little protuberant, and is perforated by a small opening, the 

 mouth. In this state it is a free, swimming, cell-like body, with 

 a crown of cilia about the mouth. The minute particles in its 

 interior move to and fro, as though acted upon by currents. 

 Next, there appear on the surface raised parallel lines which 

 run obliquely to the two poles of the mouth and opposite extre- 

 mity. The body next elongates, assuming a leech-like form, and 

 moves about in a very serpentine manner. Still increasing in 

 size, they become flask-shaped, the cilia about the mouth become 

 more perfectly formed, and there is developed about the nu- 

 cleus, which has remained unchanged all this time, a pyriform 

 sac communicating with the mouth, the nucleus being clearly 

 seen at the bottom of this sac. This may be regarded as the 

 stomach, for by the vortical action of the cilia about the mouth, 

 particles of fat, &c., are constantly drawn into it. The only 

 change, after this, is that this animal-like body becomes more 

 spherical, and quite resembles, when highly magnified, a mite 

 deprived of its legs. 



A most careful examination of its contents, with the highest 

 powers, detects no organs whatever, except the stomach ; its 

 whole body is highly contractile, and the neck equally protrac- 

 tile, and its whole movements seem quite indicative of voluntary 

 power. After all it is little else but a modified nucleated cell, 

 and however animal-like is its appearance, it cannot, I think, be 

 regarded as an individual animal, but only as the intermediate 

 condition of one belonging, it may be, to the Hchninths, or to 

 the Turhellaria, and which is living in this way in its larval or 

 immature estate. 



Mr. Sprague announced that suites of American plants, 

 containing eight hundred specimens, collected by the late 



