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XXXI. — Encystment of Tardigrada. By James Murray. (With Two Plates.) 



(MS. received May 23, 1907. Read June 3, 1907. Issued separately September 5, 1907) 



Introduction. 



The object of this paper is to discuss the recently discovered encystment of 

 Tardigrada, as far as our imperfect knowledge permits ; to compare the process with 

 that observed in certain low groups of the Acarina, in which the Tardigrada are gener- 

 ally considered to have their nearest relatives ; then to inquire whether these new 

 facts throw any light on certain puzzling facts in the physiology of the Tardigrada and 

 Acarina, such as the retrogression which produces the simplex forms of Tardigrada, 

 and which is said to accompany each moult of the Acarina ; and lastly, if they con- 

 tribute anything towards settling definitely the systematic position of the Tardigrada. 



That water-bears encyst themselves was first ascertained by Professor Lauterborn, 

 and a short note on the subject was published in 1906 (21). 



It is now known that the cysts of Tardigrada are extremely common, and there 

 is reason to believe that various naturalists have seen them, though without recognising 

 their true nature. 



Professor Richters, in a recent letter, suggests that some of Spallanzani's figures 

 might possibly represent cysts (35). 



Spallanzani's original figures I have not seen, but they are reproduced by Schultze 

 in his " Macrobiotus hufelandi" (34). Those figures are so crude that it is only by 

 making large allowances that they can be accepted as Tardigrada. Fig. 5 on Schultze's 

 plate, representing the ventral view of the animal, shows five pairs of limbs, each 

 ending in a single strongly hooked claw, two pairs of limbs terminating the body in 

 a manner hardly possible in any natural position of a water-bear. But, granting that 

 they are Tardigrada, as Spallanzani's experiments, and the situation in which he 

 found the animals, render reasonably probable, then the elliptical body represented in 

 fig. 7 as reproduced on Schultze's plate might well be a cyst. 



Schultze's own figures 2 and 3 might be cysts, or merely contracted examples. 



Doyere probably had cysts in view when he wrote, in his Memoire sur les Tardi- 

 grades, in 1840 (4) p. 308, " J'eus d'abord quelque peine a reconnaitre i'animal, dans 

 la petite masse, inert, en apparence granuleuse et amorphe que je rencontrais parfois a 

 l'interieure de certaines peaux qui me semblait abandonnees." 



No one appears to have suspected the true nature of these amorphous objects. 



I learn from Professor Richters that he had seen some of Professor Lauterborn's 

 cysts in 1906. For some years these sausage-like little yellow packages had been 



TRANS. ROY. SOC. EDIN., VOL. XLV. PART IV. (NO. 31). 121 



