1706 ON SIMPLE STRIATED MUSCULAR FIBRES, 
out with such regularity that they must be held to be due to the 
fibres being made up of alternating series of stainable and unstain- 
able segments, which, however, are not distinguishable by a marked 
difference in optical properties. 
Among the lower worms few instances of the occurrence of such 
fibres have been recorded. According to Ley dig* * * § the uterus of 
Echinorhynchus nodulosus contains in its walls transversely striated 
fibres ; but in his account of the same organ in the common species 
of the genus (E. gigas), Andresf makes no mention of striated 
fibres, and they do not occur in the only species I have had the 
opportunity of examining. Again G. R. WagenerJ described the 
muscular fibres of Nemertines as transversely striated ; but the 
striations seem to be of a very indefinite character. 
To the category of simple striated fiVjres appears to be referable 
also the striated muscular tissue found by Jourdan§ in Protula 
intestinum, in which he describes the striations as being as 
numerous and as fine as in the striated fibres of Mammals. In 
certain other Polychseta striated (simple) fibres have been 
described by various observers, but the appearance of striation 
seems to have been produced in many of these cases, if not 
in all, by the folding or wrinkling of the fibre||. In the 
muscular pharynx of Aphrodita, Lebert^ described striated fibres, 
but this is a mistake — the appearance described and figured being 
due to the crossing at right angles of two sets of simple non-striated 
* “ Lehrbuch der Histologic.” 
+ “ Weibliches Geschlechtsapparat des Echinorhynchus gigas.” ‘Morph. 
Jahrb.’ IV. Bd. 
J “ Ueber die Muskelfaser der Evertebraten.” ‘ Archiv von Reichert 
und du Bois-Reymond,’ 1863. 
§ “Sur la structure des fibres musculaires de quelques Ann^lides poly- 
chfetes.” ‘ Comptes Rendus,’ 1887. 
II Vide Rohde, “Die Musculatur der Chistopoden.” ‘ Zool. Anz.’ VIII. 
Jahrg. 
IT “ Recherches sur la formation des muscles dans les animaux.” ‘ Ann. 
des Sci. Nat. Zool.’ (3) Tome XIII. (1850). 
