838 MR JAMES MURRAY ON 



familiar to me, but I had merely wondered at them till, in the beginning of winter 

 1906-7, an opportunity occurred of seeing how they were formed. 



The cysts which I found in great abundance were of quite different forms from the 

 familiar yellow objects, and were not at first suspected of being Tardigrada. 



After watching them for some weeks and ascertaining a very remarkable series 

 of changes, a preliminary note on the subject was published in The Zoologist for 

 January 1907 (25). 



While this was in press, Professor Lauterborn's first short note on encystment 

 reached me (21). 



Encystment of M. macronyx. 



Professor Lauterborn's account of the process is brief, but of great interest. He 

 observed a water-dwelling species, Macrobiotus macronyx, Duj. On page 267 he tells 

 how he found, in many ponds around Ludwigshafen, skins of Macrobiotus which 

 appeared to be filled by a single immense resting egg. He saw also, on one occasion, 

 the body of a Macrobiotus loosen itself from its cuticle, and contract within it into an 

 elliptical body, which then secreted a closely fitting envelope. Within this shell there 

 was at first a feeble movement, which ceased in about an hour. The rods in the 

 pharynx remained visible. 



At first the cuticle of the beast remained connected with the cyst by numerous folds, 

 but later it shrank more and more together, till finally the surface of the cyst appeared 

 covered with a maze of spines and ridges, like some winter-eggs of Eotifers. The 

 stomach of the animal observed was colourless, instead of golden-brown as usual. The 

 thick skin was disposed in numerous transverse folds. 



Professor Lauterborn does not remark on retrogression, simplification, or liquefac- 

 tion of organs taking place within the cyst. 



In a ditch near the pond where he found the animal which he actually observed 

 to encyst itself, he saw many females of M. macronyx with their eggs deposited in the 

 moulted skin. 



Since the discovery that Tardigrada encyst themselves, Professor Eichters has had 

 cysts of various species under observation, and has made some interesting discoveries, 

 which will no doubt be recorded at an early date. 



Encystment of M. dispar. 



My observations were made on another water-dwelling species, M. dispar, Murray 

 (25). This is, like M. macronyx, Duj., a very large animal, attaining to nearly a milli- 

 metre in length. A lateral view of the animal is given in fig. 1. 



It is hyaline and yellow or brown, with a pair of dark eye-spots. The teeth and 

 pharynx are of the same type as those of M. hufelandi, Richters, but differ in many 



