II. A FLORA WITHIN ANIMALS. 27 



plants growing from the mucous membrane of the intestine it usually does not grow 

 more than the -^^-^ of an inch in length. 



In Enterohryus attenuatus, the pedicle is usually relatively shorter and broader, 

 and more conoidal than in Enterohryus elegans. 



In the latter, with the growth in length of the pedicle, it becomes more or less 

 transversely contorted. 



At its basis of attachment, the pedicle, when fully formed, is expanded into a 

 discoidal surface, by which it adheres with very great tenacity to its body of sup- 

 port, so as to permit rupture of the pedicle, or the principal cell, without detach- 

 ment of the former. 



_ In the very young thallus of Enterohryus, the principal cell is situated upon the 

 convex summit of its pedicle, but as the former grows and the latter increases in 

 length, the summit of the pedicle becomes depressed, and receives the convex com- 

 mencement of the principal cell in the manner of a ball and socket joint. 



The attachment of the principal cell to its pedicle is strong, and it is much easier 

 to break than to detach them from one another. 



In Enterohryus attenuatus, in two instances, I observed the pedicle, twice its usual 

 size, divided at the summit, and giving connection to two primary cells of the plant 

 (PI. IV, 27, h). These cases, of course, constituted an abnormal conjunction, such 

 as is frequently observed throughout the vegetable and animal kingdom. 



4. State of Development of Enterohryus in relation to its particular Locality of 

 Growth.^ — The most favorable position for the development of Enterohryus is the 

 commencement of the small intestine, or, more properly, the ventriculus of Julus, 

 and the transverse ridges bounding the sacculi of the ventriculus of Passalus. In 

 Julus, in the position mentioned, Enterohryus may always be found, and, in most 

 cases, with secondary cells in all stages of development. In Jtilihs marginatus, 

 lower down in the ventriculus, Enterohryus is frequently met with, but always 

 small in size, and but very rarely advanced to such a degree as to produce secondary 

 cells. Within the large intestine of the same species of Julus, it may often be 

 observed, more especially at the lower part, in the most extraordinary profusion, 

 but always in the earlier stages of growth, rarely more than the sixth of a line in 

 length, and forming a single, simple curved cell with faintly granular contents, and 

 occasionally a few small globules (PI. II. 2). 



Enterohryus elegans is frequently found attached to any part of the exterior of 

 the body of the nematoid entozoa of Julus marginatus, even upon the spiculate tail 

 of Streptostomum or Thelastomum, which has a very little larger diameter than the 

 plant itself (PL VI. 1, 2, 4-7; VII. 12, 15). Upon these worms I have never detected 

 Enterohryus advanced to the stage of development of secondary cells, and its 

 greatest length upon Ascaris infecta I found reaching to one line, but never so much 

 upon the more active Streptostomum agile and Thelastomum attenuatum. 



I never detected Enterohryus attenuatus growing upon Hystrignathus rigidus, a 

 nematoid entozoon rarely absent from the ventriculus of Passalus cornutus. 



5. Advantage of the peculiar forms of different species of Enterohryus. — One of the 

 most beautiful instances of means adapted to an end in view is presented in the 



