II. A FLORA WITHIN ANIMALS. 33 



cells, or they are found filled with a fainter granular matter and more protoplasm, 

 apparently as if much of the original granular matter had undergone solution, and 

 less frequently some are observed containing granular contents mixed with globules. 



The secondary cells do not always become detached singly from the parent plant, 

 for I have occasionally observed two and three clinging together by their extremi- 

 ties, but separated from the parent (6). 



The detached cells exhibit a remarkable disposition to reattach themselves by one 

 extremity, usually to the mucous membrane of the intestinal canal ; but, in several 

 instances, I have observed them attached to the sides of a growing thallus (5 c). The 

 law which determines the detachment of the secondary cells from the parent plant, 

 to become again attached to some other body is curious and difficult to understand. 



Besides detached secondary cells, more frequently young growing thalli of Eccrina 

 are observed, remarkable for their singular form. These consist of a primary cell 

 from the -^ of an inch to the i of a line in length, with an abrupt geniculate 

 bend in some part of its course, the upper and lower portions forming a more or 

 less obtuse angle with each other (8, 9, 11, 13), The portion below the flexure is 

 cylindrical and usually straight, but occasionally is slightly curved, or sigmoid, 

 and measures from 5-5*07 to j- 5 ;l - - of an inch in diameter. The upper or distal 

 portion is more or less dilated, cylindroid, straight, obtusely round at the end, and 

 measures from the ^oV^ to the y^ of an inch in diameter. 



The bend or flexure occurs at any point below the distal third of the thallus. 

 Sometimes the lower portion of the latter is twice as long as the upper, when it 

 looks like an oblong cell supported upon a long footstalk (13) ; in other cases, the 

 upper portion is four or five times longer than the lower (12). 



Occasionally, the young thallus observes a straight course throughout, and is 

 clavate in form (10). 



The contents of the young filaments of Eccrina consist of protoplasma with 

 faintly granular matter (12), or the same combined with a few globules (10), or 

 the lower portion of the cell is filled with the former, and the upper portion with 

 the latter (8, 11) ; or, in rather older individuals, the upper portion is frequently 

 distended with globules, while the lower contains a mixture of granules and globules 

 passing gradually into a mass of protoplasma at the lower extremity (13), or the 

 whole, in still more advanced individuals, is entirely filled with globules with a 

 very few granules and a small quantity of intervening protoplasma (7). 



The attachment of the young of Eccrina, like that of Enterobryus, is upon a 

 slight conical elevation, apparently part of the structure of the basement-membrane. 



7. DESCRIPTION OF THE GENUS AND SPECIES OF ARTHROMITUS. 



ARTHROMITIJS, LEIDY. 

 Proc. Acad. Nat. Sci., iv., 227. 



Thallus attached by means of one or more granules, simple, cylindrical, very 

 long, filamentous, articulate, without ramuli. Arliculi indistinct, with amorphous 

 contents finally converted into solitary oval sporuli. 



