jQQ LOWER INVEIlTEnRATES. 



specimens of Affcdma .vhich I luive studie.!, there ^ve>•e seventeen pairs of well-devel- 



oped iiectooalices. . , <• ' ^i 



Tlie appendages to the polypstem are somewhat different in character from those 

 of t!,e nectostem, and are of several kinds, differing in character, size, and shape. J he 

 iirst and most prominent of these are known as the covering scales. They are trans- 

 parent gelatinous bodies, and are found throughout the whole length of the polyp- 

 stem. Their shape is quadrangular or almost triangular, and they are united to the 

 axis by one anole. The upper and lower faces are flat, and the whole appendage has 

 Vthin leaf-like^1ppearance. Through its walls from the point of attachment to the 

 distal anole there runs a straight unbranched tube which communicates^ freely with 

 the cavity of the stem. The covering scales are easily detached, and are incapable of 

 voluntary motion. Their function seems to be to shield the structures which lie be- 

 neath them. , , „, 



Below the covering scales three kinds of bodies hang from the ].olypstem. They 

 are known as the polypites or feeding stomachs, tasters, and sexual bells. The polyp- 

 ites are the most conspicuous of these bodies. They have a flask-like shape, and are 

 united to the polypstem by one extremity, while the free end has a terminal ojiening 

 which is a mouth. The walls of the cavity of the ]wlypite are crossed longitudinally 

 by rows of cells which have been compared to a liver. In the cavities of the polypites 

 the half-di-ested food can be seen through the w.alls. The nutritive fluids formed 

 in these bodies are poured into the cayity of the .'ixis, there to be distributed 

 throuo-hout the different appendages of the animal. When indigestible substances, as 

 the hard parts of Crustacea, are taken into the stomach they are thrown off again 

 throu-h the mouth-opening. I haye never seen the polypites more than seventeen 

 in number, and they hang at regular intervals along the whole length of the polyp- 

 stem. . , . 



One of the most prominent bodies next to the nectocalices and covering-scales in 

 the Amilma are the so-called tentacles, which hang from the base of the polypites, 

 and which when extended are very long. The tentacles of Ac/alma are long, highly 

 flexible, tubular filaments whose function is the capture of food. At times widely 

 extended their length is little less than that of the Affcdma axis itself. At other times 

 they are drawn up under the covering-scales at the base of the polypite, and have a 

 very diminutive size. Along their whole length they are dotted with crimson pendants 

 of minute size which are called the tentacular knobs. These will be found, on close 

 study, to be of a very complicated structure. Their true function is somewhat prob- 

 lematical, but they are supposed to assist in the capture of the food. In addition to 

 the well-developed tentacular knobs which dot the whole length of the tentacles, 

 there are many half-grown bodies of the same character clinging to the base of the 

 polypite. 



Alternating with the polypites at intervals along the polypstem are found very 

 curious bodies called tasters, which have a close likeness to the flask-shaped feeding 

 zooids. These bodies are without a mouth-opening at their free extremity, while from 

 their base hangs a long, highly-contractile filament which is destitute of tentacular 

 knobs. The tasters have an internal cavity which is in free communication with that 

 of the axis of tlie animal. Various functions have been assigned to the tasters, but 

 none without objections seems yet to have been hit upon. Their usual position is in 

 clusters midway between the adjacent polypites. The term taster is somewhat mis- 

 leadino- for these bodies do not have gustatory functions. 



