J. Johnstone 
388 
The supposed striation of the muscles of the proboscis bulbs. A 
distinct striation of these fibres has been described by several authors. 
Pintner (1880, p. 51) states that they ai’e generally striated and 
comments on this condition as one of the very few instances of striped 
muscle in the phylum of the Platyhelminthes. He describes the 
proboscis bulb in Tetrarhynchus longicollis van Beneden as being built up 
of six distinct laminae in all of which the fibres are transversely striated; 
and he figures an isolated “ Muskelband ” in which there is a very 
evident appearance of banding (Taf IV, Fig. 6). The diameter of this 
structure is not given so that it is difficult to be sure whether a single 
fibre or a small group of such is intended to be represented. In a 
further paper Pintner (1893) describes a similar condition in Tetra¬ 
rhynchus smaridum Pintner, and though he admits that the striation is 
“ ausserordentlich Zarte,” and only to be seen with difficulty, his 
references and figures (p. 626 and Taf. IV, Fig. 60) appear to leave no 
doubt as to his interpretation of the structure seen in the fibres. 
Vaullegeard (1889, p. 316) describes striated fibres in the bulbs of 
Tetrai'hynclms rufficollis Eisenhardt; and Ldnnberg (1889) describes 
a similar condition in the larval form Goenomorphus linguatida (van 
Beneden) and in Tetrarhynchus tetrabothrvus van Beneden (Ldnnberg, 
1891, p. 60, Taf I, Fig. 17). There is therefore an apparent body of 
evidence in favour of the occurrence of cross-striated muscles in Tetra- 
rhynchids. Now it appears unlikely, a priori, that transverse striation, 
which is usually associated with rapidly contracting muscle fibres, 
should occur in the slowly contracting muscles of the proboscis 
bulbs and be absent in the much more mobile bothridial muscles, and 
it is worth while examining further into the nature of these structures. 
I am quite unable to find any evidence that such indubitably striated 
fibres do occur either in Tetrarhynchus erinaceus or in T. tetrabothrius 
and I can only explain the strikingly distinct figui’es given by the 
authors quoted by supposing that they have been observing artifacts. 
Pintner’s work on the Tetrarhynchids bears every indication of extreme 
accuracy of observation and I have been able to confirm almost every 
detail of structure described by him, with the exception of these so-called 
striated muscle fibres; and must conclude that the appearance is a 
spurious one. 
Such a spurious striation certainly occurs in the species now under 
description and is represented in PL XXIII, figs. 22 and 23. It will be 
seen from PI. XIX, fig. 5 that the decussation of the muscle fibres is 
exhibited very clearly in certain parts of the transverse section of the 
