4 W. F. LANCHESTER. 



Further, on opening up the body it is found that the ventral retractors arise 

 from one-third to nearly one-half of the distance between the segmental openings 

 and the end of the body, which again suggests Ph. fuscum ; but that the segmental 

 organs are very short and do not reach as far as the origin of the ventral 

 retractors, which accords with the arrangement in Ph. antarcticum. The latter 

 point is complicated by the fact that in three of the specimens the segmental 

 organs do over-reach the ventral retractors by as far again, yet are not so much 

 as half the length of the body in Ph. fuscum. And the number of coils of 

 the gut points to neither the one nor the other, as they vary from about fifteen to 

 about twenty-five (about eighteen in Ph. fuscum, about twenty in Ph. antarcticum}. 

 Turning lastly to the papillae, we find that the description of them in the other two 

 species accords fully with their appearance in this, except that here they are variable in 

 one point. Dr. Michaelsen tells us that in Ph. antarcticum they are 027 mm. wide 

 and 08 mm. high (i.e. three times as high as wide) ; in Ph. fuscum, he only says that 

 they are "bis '07 mm. lang, also nicht ganz so lang wie die entsprechenden von 

 Ph. antarcticum" but the comparison of absolute lengths where the difference is so 

 small is valueless, assuming the proportions to be the same; so that we can only' 

 conclude that they are practically identical in the two species of Michaelsen in regard 

 to this point. Now in our species the papillae in some individuals show this ratio of 

 3 : 1, but in others the ratio of the height is less (2'5 : 1, 2*25 : 1, 2 : l). 



In Ph. geoi-gianum the introvert is only half the length of the body, and the 

 papillae are much longer than in the other species quoted ; and these points, taken 

 along with other smaller differences, seem to clearly separate our form from it. 

 From Ph. lagense Fischer, these specimens are very little distinct ; but this form is 

 itself hardly to be distinguished from Ph. antarcticum. The thinness and clear 

 colouration seem to be the main distinction in most of the specimens ; and in all 

 of them the relative unimportance of the system of striation on the hind end. In 

 Ph. lagense, moreover, the segmental organs are as long as half the body. 



I subjoin a list of measurements taken from a few of the specimens ; the 

 sign " S.O." is meant to indicate the "opening of the segmental organ," and the 

 measurements are in millimetres and taken as accurately as the conditions would 

 permit. 



The letters A, B, etc., correspond to different localities, while the figures 

 1, 2, 3, etc., merely indicate different specimens. At the same time it may be 

 pointed out that the A and B specimens are all obviously of one type, viz., 

 thin-skinned and straw-coloured, while those marked E and F are those that I 

 have already mentioned as differing from the rest in general facies, viz., dark in 

 colour and apparently thicker-skinned. 



The most remarkable difference is to be found in the specimen marked E 2. 

 Here the extended introvert is much longer than the body, 26 '3 mm. and 8 '5 mm. 

 On the other hand, in the one marked E 1, which presents all the general facies 



