4 • CALIFORNIA ACADEMY OF SCIENCES. [Proc. 3D Ser. 



Wallengren (1894) holds that until the genus is more 

 carefully studied three species must be retained: Licno- 

 ■phora auerhachii Cohn, Licnofhora cohnii Claparede, Lic- 

 no-phora (auerhachii) Fabre, the latter species not being 

 identical with the one described by Cohn, The form which 

 Wallengren has worked upon, he finds upon Doris muricata 

 and regards as identical with that found on the same host 

 by Auerbach and Cohn, and by Claparede on Thysanozoon 

 tuber cula. Licnophora aster isci, from Gruber's description 

 and figures, he identifies with L. auerbachii ; but Fabre's 

 (1888) account of the rudimentary velum and ciliary mem- 

 branes of the attachment disk and of the peristomal mem- 

 branellse lead him to think that he (Fabre) was working on 

 a different species. Claparede's comparison of the two 

 forms which he describes leaves little doubt that L. auer- 

 hachii and L. cohnii are distinct species. 



These forms are all exclusively marine and occur as 

 ectoparasites or commensals on gills or tentacles of various 

 nudibranchs, annelids, etc. — Cladonema, ySolis., Aplysia, 

 Doris, Psyrtnohranchus, Syllis, Thysanozoon, Asteriscus, 

 Ophiothrix. 



Two fresh water forms have been described : the first, 

 Z. setifera, by Maskell (1886), as occurring in New Zea- 

 land; the second, as L. europcBa, by Garbini (1898) of 

 Verona. A comparison of the figures and descriptions 

 given by the two authors shows many points of mutual simi- 

 larity, but nothing whatever of the characteristic features 

 of Licnophora. Biitschli (1889) alludes to L. setifera 

 Mask, as a doubtful species, and both it and Licnophora 

 europcBa Gar. should be carefully studied before their valid- 

 ity as species of Licnophora can be recognized. 



Brief morphological descriptions of the various species 

 of Licnophora have been given by Cohn (1866), Claparede 

 (1867), W. Saville Kent (1881-1882), Gruber (i884«), 

 Fabre-Domergue (1888), Butschli (1889). The only 

 extended cytological study of Licnophora, including the 

 first account of its division phenomena, was published in 

 Swedish by Hans Wallengren, in 1894. The study was 



