2,54 PROCEEDINGS OF THE NATIONAL MUSEUM. vol.63, 



bAve been broken off, can not be found in every specimen; for 

 Ihe same reason they may have been overlooked in B. mirus. The 

 papilla at the base of the first lateral cirrus does not appear to 

 be present in B. caudatus at all. The sense organ at the base of 

 the last lateral cirrus is described as rod-shaped or club-shaped in 

 B. viirus. In preserved specimens of B. caudatus it has the appear- 

 ance of a rod but on close examination proves to be a thin flap with 

 a slight spiral twist. In B. mirus there is some evidence that the 

 sense organ is similarly formed. 



The marine tardigrades are of special interest, as has been pointed 

 out by Professor Richters in the articles already cited, in that they 

 furnish conclusive evidence that the group Xenomorphida (=Tardi- 

 grada of most writers) is an offshoot from the chaetopod worms 

 and is not at all closely related to the Arachnida near which 

 it is placed in nearly every textbook on zoology. The legs of the 

 bear animalcules are properly to be regarded as modified parapodia 

 and the claws and toes are specialized setae. The cirri of the head, 

 especially those of Ilalechiniscus and BatilUpes find their counter- 

 parts only among the Chr.etcpoda. 



Five exclusively marine genera of bear animalcules are now 

 known. A sixth, Macrohiotus contains at least two species which 

 live in the ocean, several which inhabit fresh water, and a number 

 which are terrestrial. The genus Milneslum is represented by only 

 one species and this inhabits fresh water. The genus Diyhascon 

 contains aquatic (fresh water) and terrestrial species. The genera 

 Orcella and Echiniscus^ the former with one and the latter with 

 forty or fifty species, are terrestrial and are found on moss and 

 lichens. Thus of the ten known genera, six are wholly or partly 

 marine and only two are strictly terrestrial. This fact points 

 strongly to a marine origin for the group and, taken in conjunction 

 with the homologies pointed out hy Professor Ivichters, goes far to 

 support his belief as to its affinities. 



EXPLANATION OF PLATE 33. 

 BatilHpes caudatus Hay. 



Fig. 1. Lateral view. 



2. Jaw^q lateral cirrus of head with flap-like appendage at its base. 



3. Detail of foot. 



4. Female, dorsal view. 



