92 



MH. E. C. BOUSFLKLD OS THE 



The first description of any species of Bero is to be found in 

 the ' Insecten-Belustigung,' iii. Theil, of Eosel von Rosenhof (24*), 

 published in 1755. Several figures and a lengthy description 

 are there given of a species identical with Dero fiircata, under 

 the name of " das geschrneidige Wasserschlanglein mit zwey 

 Grabelspizen." The remarkable feature of Kosel's account is 

 the moniliform arrangement of the two long palpi by which 

 this species is distinguished, which he described. This character 

 has not been noticed by Grebincky, Semper, or myself; but 

 the explanation is not far to seek. One of the first signs of 

 approaching dissolution in the Naid family is the separation of 

 the cuticle from the cells of the epidermis, with formation of 

 hullce ; and under these circumstances something of the kind 

 has been observed by the writer. It is somewhat curious 

 that up to 1877, when the last description of this species was 

 written, every observer who described the form gave it a fresh 

 name ; so that it has received trivial names from, its discoverer 

 and from Miiller, and scientific ones from Oken, Grrebincky, 

 Leidy, and Semper. Hosel observed the process of transverse 

 fission in an advanced stage, and described it as a "curious 

 method of copulation." He also described the result of transverse 

 sections of the worm. 



Following Rosel, the distinguished naturalist 0. F. Miiller (18), 

 in 1771, gave a remarkably excellent account of one or two 

 species ; all the main features having been grasped, and the 

 branchial processes (the characteristic feature of the genus) 

 having had their proper function assigned to them. In specific 

 characters, however, Muller was less fortunate ; and to him must 

 be given the blame of the confusion in the nomenclature of the 

 genus which so long existed. In consequence of the small scale 

 on which his figures are drawn, there is great difficulty in identi- 

 fying the species represented ; but two, if not three, distinct ones 

 are certainly shown, all being included under tlie general name 

 of JVais digitata. Eosel's species is recognized as distinct, 

 and named " the eyeless Naid with pronged tail," the other 

 being called " the blind Naid with fingered tail." The distinc- 

 tion thus formulated is too slender to enable me to decide 

 as to the specific differences ; and in view of the impossi- 

 bility of ascertaining the particular species to which Miiller 

 intended to apply the name digitata, there seems to be no 

 * The numbers in brackets refer to the Bibliography, p. 106. 



