Haswett—A Monograph of the Temnocephalee. 109 
VII.—Tue Parencuyma. 
The complex ramifications of the nerve-tubes, the branches of the excretory 
vessels, the unicellular glands and their ducts, and the bands of muscular fibres that 
extend from one surface of the body to another, or from organ to organ, take up so 
much of the space between the body-wall and the digestive and reproductive organs 
that the quantity of parenchyma is not relatively very great. Where it occurs 
uncomplicated by other elements, it presents the appearance of a close reticulum of 
delicate fibres, which, where they anastomose, sometimes present plate-like expansions. 
Dotted here and there at wide intervals are to be found oval nuclei ‘012 mm. in 
diameter (Pl. x. fig. 9), which seem to be the only nuclei specially appertaining to 
the parenchyma proper. In osmic acid preparations the meshes of the network are 
found to be oceupied by a more delicate reticulum. To judge by its behaviour under 
the action of staining agents, this network of fibres is not of protoplasmic character, 
having undergone a sufficient amount of modification to render it incapable of being 
readily coloured. It is likely that the whole tissue in the living animal is filled like a 
sponge, not with hyaloplasm, as stated by Béhmig with reference to the Rhabdoceeles, 
but with a watery fluid containing a certain amount of coagulable matter. Probably 
the parenchyma is to be regarded as composed of large cells with the nuclei above 
described, without cell-boundaries, and with a protoplasmic reticulum which has 
become greatly vacuolated. 
In addition to the cells already described and those to be referred to later as 
excretory cells, there occur embedded in the parenchyma, here and there throughout 
the body, groups of cells which appear to have no connection with any of the systems 
of organs, and which I referred to in my former paper as parenchyma cells.* These 
(PIL. x. fig. 10) are comparatively small cells, about ‘01mm. in diameter in 7. fasczaza, 
which occur rarely singly, nearly always in clumps of ten or twelve closely aggregated 
together. They have oval nuclei 0025mm. in long diameter, with a minute spherical 
nucleolus and other smaller scattered particles of chromatin. In several cases they 
were observed to be dividing with mitosis. They are very like the nerve-cells but 
much smaller. 
In the parenchyma of certain- of the species— 7. fasczata, T. quadricornis, T. 
minor, T. Nove-zealandie—there is more or less pigment. In 7. fasczata this is very 
abundant—chiefly taking the form of a fine close network of very delicate threads of 
* Braun inadvertently states that I described the parenchyma cells as star-shaped. This is not the case ; I did not 
give any special account of them. The star-shaped cells which appear in several of my figures correspond to what are 
described in the present paper along with the excretory system. 
