350 



on the 'Challenger' Collection'^, remarks that although some species 

 are devoid of suckers "it Avould be desirable to place this beyond a doubt 

 by the help of sections, since it is always possible that (except in Stele- 

 chopus and the encysted species there may be microscopic rudiments of 

 suckers remaining; and on the other hand, it is possible that certain 

 ■cavities on the ventral surface of many species do not really represent 

 suckers at all, as they were formerly supposed to do. 



It seems also the limit of the suckers and their appearance generally 

 varies according to the different state of contraction in which they are." 



I have carefully searched through the literature and examined the 

 figures of described species of Myxostoma in some detail, as the result 

 I feel confident that one species at least possesses more than four pairs 

 of suckers. This is M. moebianum v. Graff, from Fouquet Island, south 

 east of Mauritius. The species was described ^ from some sketches, 

 notes and preparations sent to the author by K. Mo e bin s in 1877. The 

 preparations were very badly preserved with the exception of the hook- 

 apparatus, and von Graff follows Moebius's notes in his description; 

 he also reproduces his drawing of the animal " and it is to this drawing 

 that I particularly wish to refer. Moebius's sketch distinctly shows 

 five pairs of suckers the last of which occupies a similar position to the 

 sixth of Mr. Crossland's specimens, i.e. between the last pair of para- 

 podia and the hinder end of the body; the remaining four pairs are in 

 their usual position between the parapodia. 



In the written description, however, von Graff says: "Of the five 

 pairs of suckers figured by D^'Moebius, one pair seems to me to be 

 really the male generative aperture" and he labels the third pair of 

 suckers in the figure cf. He gives no reason for this step, nor does he 

 ■explain why he singled out this particular pair; all the suckers are 

 drawn alike and there seems no reason to doubt the accuracy of 

 Moebius's sketch. 



Moreover, if we accept von Graff's conclusion that the third pair 

 of suckers represent the penes we find that the remaining four pairs are 

 in an abnormal position, thus the last pair is behind instead of in front 

 of the last pair of parapodia. 



I have reproduced the figure in question, and I think there can be 

 no doubt that M. moebianiini really possesses five pairs of suckers. 



It is possible that additional pairs of suckers have been overlooked 

 in other species, being either very inconspicuous or rudimentary and 

 only visible in sections or in mounted specimens. 



Ö L. V. Graff, Report on the Myzostomida . . . Zool. Challenger Exp. 

 Part XXVII. 1884. p. 10. 



"■' L. V. Graff. T. c. p. 48. - T. c. pi. VIIT. fig. 3. 



