J. MURRAY ON GASTROTRICHA. 213 



deliberately ending the individual life which we have before our 

 eves, intelligent, and surely innocent, I confess that, old and 

 hardened as I am at the game, I feel guilty of murder. 

 My ideal is that realised by Mr. Bryce, with his " zoo " of 

 Rotifera, all kept alive in cells, visited again and again for weeks 

 and months, till they become old familiar friends, each known by 

 sight and name : where a death in the family is regretted, and 

 the beasties, in fact, reach a ripeness of old age which must be 

 rare under natural conditions. 



I wish to thank Mr. Rousselet and Mr. Bryce for the assistance 

 they have given me in preparing this paper, by lending me 

 specimens and books, and Mr. Harring for bibliographical refer- 

 ences and extracts from works which I had not seen. 



Form axd Structure. 



AH Gastrotricha are built on a very uniform plan. Most of 

 them have a roundish, often 3- or 5-lobed head, a more or less 

 distinct neck and a slightly expanded body, diminishing pos- 

 teriorly to a usually forked, but sometimes undivided extremity 

 {tail or foot). The principal external features are : the tubular 

 mouth, certain sensory hairs on the head, various forms of scales 

 and hairs clothing the dorsal surface. The ventral surface is 

 traversed for its whole length by two bands of vibratile cilia, by 

 which the creatures can creep in the manner of an Adineta, and 

 sometimes even, apparently, swim. A few possess clear bodies 

 which have been supposed to be eyes. 



Of the internal structure I shall say little, as I have given it 

 little study, and I can only quote from authors who have studied 

 it. The animals are on about the same plane as the Rotifera for 

 complexit}', but they look much simpler fewer organs are readily 

 visible. A casual examination shows only a thick skin and the 

 body cavity, through which passes the simple alimentary canal ; 

 the slender oesophagus passing through an oblong muscular 

 pharynx ; the expanded stomach (or intestine) occupying most 

 of the body cavity. There is a small intestine, from which the 

 anus opens at the base of the furea, on the dorsal side. 



Several naturalists have detected a water-vascular system 

 somewhat like that of the Rotifera, but according to Zelinka 

 it differs in many points. The canals are much convoluted, 



