116 Prof. M'Intosh's Notes from the 



proboscidian sheath, which is shown in Hubrecht's figure, has 

 been omitted, to the confusion of the student. 



Besides the foregoing, the text-books omit reference to the 

 lateral vessels of the proboscidian sheath in certain forms, the 

 remarkable structure of the proboscis of the various groups in 

 section, the acid reaction of the skin in many, and other 

 points. The assertion that the proboscis is clearly an offen- 

 sive organ, on the faith of the problematical u nematocysts," 

 while nothing is said as to its being so readily thrown off and 

 so slowly regenerated, requires modification. That the 

 Nemerteans " extract " tubicolous worms by this organ is a 

 statement in need of confirmation, especially in view of 

 Prof. Hubrecht's notion of the " large amount of nervous 

 tissue in its walls." So far as my experience goes, the 

 tubicolous worm would more readily " extract" the proboscis. 

 The statement (after Hubrecht) that the albuminoid material 

 embedding all the layers of the body is of the nature of the 

 jelly of Medusae demands a dissenting note, as also the 

 remark that the small specimens swim freely. What of 

 Cerebratulus angulatus, a yard long and an inch broad? No 

 fish more deftly cleaves the water. The remark that the 

 central stylet of the proboscis is either pointed or serrate is 

 too indefinite, though perhaps less in error than that clause 

 which asserts that the aperture for the proboscis is close to 

 the mouth. Even for the Enopla the latter will not hold, 

 while for the three groups of the Anopla it is wholly at 

 variance with fact. 



In changing systems of classification it is usual to give 

 reasons for laying aside those already established, e. g. either 

 the prevalence of error or the advance of discovery which 

 upsets the foundation on which the older superstructure was 

 raised. In the case of the Nemerteans neither the one nor 

 the other has a substantial basis. The essential anatomical 

 features on which the classification of 1869 and 1873 was 

 based remain to-day as they were then. Yet we have had 

 the run of Prof. Hubrecht's Paleeonemertes, Schizonemertes, 

 and Hoplonemertes, to the confusion of the student ; and now 

 Dr. Burger's Protonemertini, Mesonemertini, Metanemertini, 

 and Heteronemertini, by way of ringing new changes, sweep 

 the former out of sight. It is immaterial, for there is little 

 to choose between them. Both simply give new and complex 

 names to the same groups which were formed on structural 

 grounds in 1869, and every anatomical fact of primary 

 importance in which remains unassailed to-day. There is no 

 need to alter either figure or description now. Yet it seems 

 to be necessary for all these old facts to be incorporated more 



