202 HENRY LESLIE OSBORN 



tudiiial muscles pass forward they ultimately meet the oral field 

 almost vertically to its surface and attach there so that they thus 

 become its retractors. Fig. 5 is a camera drawing from a speci- 

 men which died with the oral field retracted. In this section the 

 longitudinal parenchyma muscles can be traced forward directly 

 to the in-bent parts of the field. Observations of sagittal sec- 

 tions furnish evidence that, at least in many cases, a single muscle 

 reaches across from the dorsal to the ventral surface, for nucleated 

 myoblasts can be seen in connection with these muscles and these 

 are grouped in the center of the body. 



Some cytological features are well shown in the muscles of 

 Clinostomum. Both the inner longitudinal wall muscles and 

 the longitudinal parenchyma muscles frequently show transverse 

 subdivisions into stained and unstained zones such as has been 

 noted in other forms by various writers on trematode histology, 

 but in no case with which I am familiar are they shown so dis- 

 tinctly as here. Nickerson ('95) states that in Stichocotyle the 

 longitudinal muscles of the body wall appear to be tubular ''with 

 nodes of deeply staining substance filling the lumen at intervals," 

 and shows the appearance in fig. 16 of his paper. Stafford, too, 

 in Aspidogaster ('96, fig. 26) noted the presence of 'transverse 

 lineations' in the parenchyma muscles which he speaks of as 

 'contraction centers.' He does not note any in connection with 

 the body wall muscles. Bugge ('02) in his paper on the excretory 

 system in cestodes and trematodes incidentally mentions 'Quer- 

 streifung der Muskelfasern' which he observed in the circular and 

 longitudinal muscles of redias and cercarias, "wie wir sie bei 

 Arthropoden und andern Wirbellosen auflanden," and also quotes 

 Cerfontaine, to whose article (in Bull. Acad. Sci. Belg., 27, no. 6) 

 I have not had access, and Nickerson as having seen the same thing. 

 In 1904 1 saw and recorded ('94, figs. 11 and- 12) a similar muscular 

 structure in Cotylaspis, a form related to Stichocoytle and Aspi- 

 dogaster. 



Turning now to Clinostomum, figs. 9, 10 and 11 are from immer- 

 sion objective camera drawings of longitudinal wall and paren- 

 chyma muscles. Figs. 9 and 11 are from the body wall and 

 parenchyma muscles respectively from the same series. Both 



