lO NATURAL SCIENCE. January. 



There is a^ small parasitic animal, whose affinities can hardly as yet 

 be considered fully determined, but which is well known as a parasite 

 in and upon crinoids, and is called Myzostoma. A species of this 

 enters the mouth of Asterias vichaydi, and, taking up its abode in the 

 blind extensions of the stomach that pass into the arms, it there 

 grows to a size and breadth that are quite remarkable tor a Myzostoma. 

 The Asterias soon feels inconvenienced, but, being unable to get rid of 

 the intruder by the way through which it entered, it is compelled to 

 adopt the rather severe measure of getting rid of the arm in which the 

 Myzostoma has esconced itself. The more numerous the parasites, the 

 greater the number of arms that have to be disposed of in this sum- 

 mary fashion. At first the starfish, endowed as all starfish are with 

 strong powers of recuperation, re-grows all its six arms ; but after a 

 time it finds it less trouble to close up the gap, and to content itself 

 with five arms. And since by these repeated struggles in its youth its 

 powers have been reduced to a greater extent than is customary in 

 this class, it often finds itself forced to hobble out the remainder of its 

 days with the miserable allowance (for a starfish) of three arms. The 

 same parasite is found to occur in Stolasterias neglecta, another starfish 

 with the same distribution, and it appears to have like effects. This 

 case of autotomy or self-division has, then, no connection with repro- 

 duction ; it is a simple example of a continuous struggle for life. 



The complete account of this will be found in Dr. von Maren- 

 zeller's report on the Echinoderma collected in the Mediterranean in 

 1893-4 {Denkschy. Akad. Wicn, Math. -Nat. Classe, Ixii., pp. 123-148, 

 1895). 



An Eastern Question. 



What has Japan got to do with the IJast Coast of America ? 

 More than once of late have we drawn attention to curious instances 

 where the distribution of a genus was confined to these two localities 

 (vol. viii., p. 10, the Chimaeroid Hariotia, and p. 350, the Octopod, 

 Opisthoteuthis) ; and now, on glancing at Dr. Sluiter's recently-issued 

 Catalogue of the Starfishes in the Amsterdam Museum, we note that 

 the well-known species Echinaster spinosus, hitherto known only from 

 the east coast of America, has — if labels are to be trusted — been 

 found on the shores of Japan. 



A Revision of North American Slugs. 



A PAPER recently published by Messrs. H. E. Pilsbry and E. G. 

 Vanatta in the Proceedings of the Academy of Natural Sciences, 

 Philadelphia (1896, pp. 339-350) marks a great advance in the study 

 of North American slugs, and forms the first of a series which will 

 prove invaluable to all interested in those animals. Writers on the 

 slugs of America have hitherto been accustomed to distinguish them 

 according to their external characters, an imperfect method of work 



