INFUSORIAL ANIMALCULES. 47 



in these figures. The minute circles at c represent several fleshy masses, which 

 are arranged two and two at the base of each arm, and are supposed to be 

 centres of the nervous matter provided for each member. The position of the 

 mouth is indicated by the letter/, and below it, at g, is the stomach, which is 

 comparatively large, and is here exhibited filled with many of the smaller 

 Infusoria. The jaws of the Stephanoceros are furnished with teeth, with which 

 it is seen to tear and masticate its food. Two distinct sets have been discovered 

 on each jaw ; of which, in their natural position, figure 68 is 

 a highly magnified representation. The lower set is seen at 

 a, and the upper at b ; the latter appear to consist of two on 

 each side ; but they are not all seen in the figure, for the 

 actual number is eight, four upon either jaw. So fierce and 

 voracious is the crowned animalcule, that it attacks and seizes 

 the Stentor with its long and flexible arms. 



The Stephanoceros increases by eggs, which are hatched before they pass 

 from the animalcule into the cavity of its transparent case. The progressive 

 development of the young, during the first stages of their existence, has been 

 studied by Dr. Mantell with the most patient assiduity. This gentleman observed 

 that the young Stephanoceros, three hours after it had escaped from the egg, 

 swam freely in the surrounding water ; in thirty hours a group of five buds 

 were beheld, which were regarded as the bases of the five branching arms con- 

 stituting the crown ; in eighty hours they were fringed with cilia, and the 

 position of the stomach was detected by the color of the food which the young 

 animalcule had swallowed. 



The specimens of the crowned animalcule, which are represented in the above 

 figures, belong to a species obtained by Dr. Mantell from a lake in the vicinity 

 of London. A supply of them was kept without any difficulty in glass jars of 

 water, containing aquatic plants, during the residence of this gentleman at 

 Clapham. But upon removing to another place, these interesting creatures 

 died, although they were furnished with their native water, and every precaution 

 was taken to ensure their lives. This mortality is attributed by Dr. Mantell to 

 a difference in the local influence of the atmosphere. 



THE BEADED MELICERTA, OR FOUR-LEAVED ANIMALCULE. This minute crea- 

 ture, which is delineated in figures 69, 71, and 72, belongs to the same family of 

 Infusoria as the Stephanoceros. It possesses, when young, two eyes, a tubular case, 

 and a single rotatory organ, which, when expanded, presents the appearance of 

 four leaves, fringed with numerous cilia, as shown in the figure. Below this 

 complex apparatus the mouth is situated, the jaws of which are armed with 

 rows of teeth, which are discerned in figure 69, near the centre of the leaves ; 

 but are exhibited more highly magnified in figure 70. This animalcule has been 

 found to be endowed with a nervous system ; and two tubes are situated near the 

 neck that apparently subserve the purpose of respiration. 



The body of the Melicerta is transparent, but the enclosing cell is of a brown- 



