ANIMALCULES WITH SHELLS. 79 



XIV. 



ANIMALCULES WITH SHELLS. THE BRACHIONUS, OR 

 SPINE-BEARING ANIMALCULE. 



THERE is yet one kind of animalcule undescribed, 

 in the drops of water which have afforded us so many 

 interesting objects for investigation. This belongs to 

 the group of Rotifera which have their bodies pro- 

 tected by a firm sub-cylindrical shell, or carapace. Its 

 form is that of a vase, with a retractile forked pedicle 

 proceeding from the base. There are two species un- 

 der view, (pi. xii, figs. 1,2). 



I. The PITCHER-SHAPED BRACHIONUS, (B. urceolaris, 

 pi. xn, fig. 1). This species has a smooth shell, with 

 six short horn-like processes, or spines, on its front part, 

 and the lower end rounded. The body is white, from 

 one-sixth to one-eighth of a line in length, and fur- 

 nished on the upper part with a pair of lobed rotatory 

 organs, composed of five portions. The jaws have five 

 teeth at the free extremity, and may be regarded as 

 dental hammers divided into sharp spines, which crush 



