846 MR JAMES MURRAY ON 



It is proven to be incorrect in various groups, so that Megnin's wide generalisation 

 breaks down ; but, considering the different extent to which retrogression goes during 

 the hypopial encystment of such closely related species as Glycophagus domestieus and 

 G. spinipes, it seems to me that each species must be independently investigated, and 

 that it is not improbable that the change may go so far in some species as to reduce 

 them to almost as simple a condition as an egg. 



It may be that the reversion to an amorphous condition which G-udden and Megnin 

 believe to accompany each moult, and the encystment in the penultimate-nymphal 

 stage described by Michael, may be simply different interpretations of the same facts. 



The Moulting of Tardigrada. 



That Tardigrada cast their skins was known to Goeze, the first naturalist who has 

 recorded an observation of a Water-Bear. Most subsequent observers have confirmed 

 the observation, and many of them noticed that some species deposited their eggs in the 

 skin which they cast. 



C. A. S. Schultze is the first naturalist, so far as I know, who has paid any 

 attention to the number of moults, and the only one who claims to have followed an 

 individual from birth to death. He states (34), p. 4, that M. hufelandi moults twice, 

 lays its eggs after the second moult, then dies. It must be remarked that an animal 

 studied in this way cannot be under its normal conditions, and death might be 

 premature. 



Doyere (4) gives a minute account of the casting of the skin, and says that the 

 epithelium of the alimentary canal is also cast, as may be seen at both ends of the canal 

 when the animal contracts greatly within the old skin. He states that they moult 

 several times, but admits that he never watched an individual throughout life, and 

 cannot state the number of moults. 



I can find no one else who has even considered the question of the number of moults, 

 though several have carefully studied a simple moult. 



Lance (20) considers Doyere's observations and conclusions as incorrect in many 

 particulars. He regards Doyere's account of the shedding of the chitinous lining of 

 the gullet and cloaca as greatly exaggerated, and on p. 44 he quotes Erlanger (12) 

 to show that a portion of the ectoderm is included in the anal invagination, and supposes 

 that it is this part only, really belonging to the ectoderm, which is shed with the outer skin. 



Except in the genus Echiniscus, no Tardigrada are known to undergo any meta- 

 morphosis. They are hatched in the final form and simply increase in size and 

 attain to sexual maturity. On this account it would only be possible to ascertain the 

 number of moults by watching the individual throughout life. In the Acarina, where 

 each moult is characterised by a greater or less change of form, it is a simpler matter 

 to count the moults. 



The metamorphosis in the genus Echiniscus is a very slight thing. The larvae are 



