ON DIPLOZOON NIPPOXICUM, N. SP. 161 



beneath the basement membrane. They run isolated without form- 

 ing bundles. This layer is most strongly developed at the anterior 

 extremity of the body in the region of the anterior suckers, and im- 

 mediately anterior to them, especially on the ventral side (Fig. 9), 

 where its thickness amounts at some places to 0.01 mm. In the 

 posterior part of the body it is very weakly developed, and in 

 the region of the posterior suckers the fibres ai*e very difficult to 

 detect. 



Closely applied to the circular layer of muscles run fhe second 

 or diagonal fibre« (Fig. 10). In the anterior half of the body these, 

 like the transverse fibres, run isolated without forming bundles ; 

 and those coming from opposite sides of the body cross each other 

 at an angle of nearly 120°. In the posterior half of the body, this 

 layer is strongly developed in the region of the folds already men- 

 tioned, where the fibres run in flat bundles and close to one another. 

 According to Taschenberg,^-" the diagonal fibres are situated inner- 

 most in Tristomum ; but in all the species of ectoparasitic Trematodes 

 I have hitherto examined, viz., in Microcotyle, Axine, Octohothrmm,-^ 

 Dactylogyi'us, and a new genus not yet named, the diagonal fibres 

 are situated between the transverse and longitudinal muscular layers. 

 Lorenz, ^^ who includes the transverse and diagonal muscles under 

 one head, also places the "zarteren Fasern " (by which he means the 

 two sets of muscles just mentioned) outward ; and an examination of 

 the sections of Tr. molae, kindly placed at uiy disposal b}' Prof. Ijiuia, 

 has convinced me of the error of Taschenberg, occasioned perhaps by 

 the circumstance that in Tristomum the longitudinal fibres describe a 



1) Taschenberi;- — Beiträge zur ICenntniss ectoporasit iseher mariner Trematoden. Halle, 

 1879. p. 11. 



2) In a species of this genus wliich I have examined, there are in addition isolated longi- 

 tudinal fibres between the diagonal and circular uiuscles. 



3) Lorenz — Ueber die Organisation der Gattungen Axine u. Microcotyle. Arbeit, a. d. 

 zool.-zoot. Inst. d. Univ. Wien etc. Bd. I. 1878. 3. Heft. 



