4 NATURAL SCIENCE. July. 



The opinion of Munier Chalmas that this so-called abnormality was 

 a sexual character was commented on adversely by Messrs. Buckman 

 and Bather, who regarded it as one of the characters of old age, 

 and we now note that Dr. Pompeckj comes to a similar conclusion. 

 His paper also deals with the question of resorption or absorption of 

 the body-chamber in course of growth. This idea was put forward to 

 explain the occurrence at the same localities of very different-sized 

 Ammonites of presumably the same species, the smaller with 

 " abnormal " body-chambers, and the larger (the presumed adults of 

 the smaller) with normal coiling at the diameter of the smaller. 

 Dr. Pompeckj, however, rejects such absorption as a principle of 

 Ammonite growth, and explains this concurrence of forms by 

 Dr. Walther's doctrine of dispersal after death (Nat. Sci., iv., 

 p. 245), intimating that all such specimens, whether big or little, 

 are full grown. But there are other difficulties in connection with 

 this, which Dr. Pompeckj 's hypothesis does not seem to meet ; and 

 his conclusion (p. 289) that " an Ammonite with abnormal body- 

 chambers is, almost without exception, to be considered as full grown," 

 may not be readily accepted. Other opinions of Dr Pompeckj's will 

 no doubt be challenged, and exception might be taken to the applica- 

 tion of the term " abnormal " to that which is a normal process of 

 growth in racial or individual decline, and which even when carried to 

 excess, as in Macvoscaphites, scarcely deserves to be called an abnor- 

 mality. All the same, the work is a notable addition to Ammonite 

 literature. 



AUTOTOMY IN ECHINODERMS. 



The obscure processes of budding and regeneration are at least as 

 interesting as the nature of variations. It is a well-known text-book 

 fact that Echinoderms have considerable power of recuperating 

 external injuries, to such an extent, indeed, that a single arm torn 

 off a starfish is said to reproduce the whole animal. It is also 

 generally believed, and in some cases known to be true, that these 

 animals can of their own accord break off or eject portions of their 

 body, which may, in a few instances, form new individuals. We 

 wish to direct attention to two observations, which, though not very 

 recent, seem, owing to the places of their publication, not to have 

 attracted the attention they deserve. 



In the fifth volume of the Proceedings of the Liverpool Biological 

 Society (p. 81), Mr. H. C. Chadwick describes how he placed three 

 individuals of the holothurian, Cncumnria planci, in a jar, and how 

 a strange thing happened to each of them. The middle portion of 

 the body was pulled out and became very thin, till at last the animals 

 broke in two. Then the front halves crawled away, " leaving their 

 tails behind them " motionless. Each front half developed a new anus, 

 and each hinder part developed a new mouth and circlet of tentacles. 

 Then one of the animals derived from a hinder part divided again, 



