Anatomical structure of Aspidogaster conchicola. 487 



aod finer bands, the cell-boundaries become stretched and thin, and 

 even, in places, unrecognizable. 



Immediately round the included organs the parenchyma comes to 

 be much compressed and passes, often, into a more fibrous structure ; 

 e. g. where the uterus folds back and forth, the cells are lengthened 

 in the same direction and compressed between its neighboring parts. 

 Anywhere in the body-parenchyma may be found, here and there, 

 protoplasmic cells, sometimes in strings passing outwards, that have 

 not undergone the same rapid change as the bladder-parenchyma 

 surrounding them. 



In the penis-sack the parenchyma is composed of much smaller 

 cells than in the body; while in the ventral sucker, and round the 

 mouth it retains more of its embryonic nature. 



Reference will have to be made to the parenchyma in describing 

 numerous other organs, but one point belongs here which, as yet, has 

 received little attention. If the so-called subcuticular cells form the 

 chief centre of growth of the animal, then, as they are situated in- 

 side the muscle layers, what is the nature of the elements lying 

 between the muscle layers, and between the fibres themselves, forming 

 the filling tissue between cuticle and subcuticular cells'? If this is 

 also subcuticula cells then we shall have to distinguish different kinds 

 of these cells. These elements are in Aspidogaster extremely small 

 and indefinite but in some places it seemed evident that there were 

 parenchyma cells present similar to those on the inner side of the 

 subcuticular layer or probably more nearly similar to those compressed 

 cells that bound the organs. Should this be found true, then the 

 term "subcuticular cells" is misleading as characterizing a layer of 

 cells lying at some distance from the organ which gives them their 

 distinctive name. The same is true of some of the other terms 

 enumerated at the beginning of this section. Some of these terms 

 (kleinkernige Zellen, chromatophile Zellen, Matrixzellen, Körnerschicht), 

 however, if suggested to their authors by the same histological cha- 

 racteristics which have come before me, and to some extent warranted 

 their application , are also suggestive of the probability that those 

 authors had before them cells retaining the power of division. Some 

 have spoken more definitely for this view e. g. Leuckart, in several 

 places (Parasiten des Menschen, Lief. 4, 1889, p. 188, 414), compares 

 these cells in Dist. hepaticum and Dist. pulmonale with parenchyma 

 cells of Cercariae and describes them as elements "die ihre Entwick- 

 lungsgeschichte noch nicht abgeschlossen haben". Looss (Zur Frage 



