172 WHEELER. [Vou. IX. 
width. Between them lie minute and much elongated nuclei, 
which, I believe, belong to them, notwithstanding the almost 
unanimous assertion of writers that the adult muscles of 
the Dendroccela are enucleate. As I have made no macera- 
tions of these muscles, I can make no definite statements in 
regard to their method of termination and attachment. They 
do not pursue a very long course as discrete fibres, but appear 
to anastomose at intervals, thus forming a net with very much 
elongated meshes. 
Beneath the delicate transverse muscles lies a very thick 
layer of longitudinal muscles (Fig. 107/), which consist of 
distinct and quite regular bundles. These extend from one 
end of the body to the other, without or with very rare anasto- 
moses. They appear as clear strands in stained preparations. 
On an average they are about 1.3 w in breadth, with a dorso- 
ventral diameter of 3. Measurements, of course, vary greatly 
according to the state of contraction of the fibres. In many 
of my preparations a peculiar striated or lamellated appearance 
may be observed in the muscular substance (Fig. 10). It seems 
to be due to an alternation of dense and stainable with an 
unstainable and more liquid plasma. The lamellz are usually 
arranged parallel to the surface of the body or at a slight angle 
to it. I fail to find any nuclei in the longitudinal muscles ; 
the nuclei which lie between the strands, often in very regular 
rows, and immediately beneath them, belong, as I have said, 
to the hypodermis. 
In B. candida the longitudinal muscles are very poorly 
developed as compared with those of S. pellucidum. The 
dorsoventral muscles, so well developed in the former species, 
are so difficult to resolve in the latter that I am not sure that I 
have seen them. Owing to its small size, Syucelidium is not 
avery favorable object for the study of the various muscle- 
layers of the pharynx and penis. 
3. Parenchyma. 
So much space in the body of Syacelidium is taken up by 
the longitudinal muscles and viscera, that the parenchyma — 
abundant in many other Triclads — is here very much reduced 
