4 T. KOMAI : STUDIES ON TWO ABERRANT CTENOPHORES 



STRUCTURE AND DEVELOPME>^T OF CCELOPLANA. 



Historical Remarks. 



In 1880, KowALEVSKY read before tlie Sixth Assemblage of the 

 Russian NaturaHsts and Physicians a paper on a remarkable animal 

 which he discovered in the Red Sea and named Codoplana inetschni- 

 kozuii. A short abstract of the paper was given by A. }5randt in the 

 '■^ Zoologischcr Anseiger" (p. 140) of the same year. The animal was 

 stated to be perfectly alike a planarian, but it showed some features 

 characteristic of the Ctenophora, so that the author regarded it to be 

 an intermediate form between the Coelenterata and the Planariae. In 

 the following year, 1881, appeared the author's second work that 

 contained a somewhat fuller account of the animal, as well as a fine 

 sketch of its general habitus. However, probably owing to its having 

 been published in Russian and in a journal of difficult obtainment, 

 the work seems to have remained unknown to many subsequent writers. 

 The material which formed the basis of both the papers consisted 

 of a single specimen, and this seems to have been examined only in 

 a superficial way. Anyway the papers deal mainly with external features 

 of the animal, and are not without passages which seein to rest on 

 insufficient or erroneous observations. They remained, however, the only 

 original records of the peculiar animal down to the time of the appearance 

 of Abbott's papers. 



Apropos of his argument on the phylogeny of the Polyclada, Lang 

 ('84) regarded Coeloplana, known to him from Brandt's abstract in the 

 ^' Zoologischer An^eiger" , regarded Coeloplana as a form representing an 

 intermediate stage in the evolution of the Turbellaria from the Ctenophora. 

 It appears that this work- of Lang's made Coeloplana widely known to all 

 zoologists as a remarkable form of high interest in its systematic positson. 



In 1902 AnnoTT wrote a preliminary account of two Japanese 

 species of Coeloplana obtained at Misaki, which he described under the 

 names of C willeyi and C mitsnkurii. In 1907 the same author published 

 a fuller paper on the animals especially dealing with their internal 

 anatomy in detail. This paper brought many new important facts to 

 light, thus greatly supjjlementing our knowledge of the genus derived 

 from Kowalevskv. Nevertheless, there still remained many points in 

 the morphology^ of the animal requiring further investigation. Recentl}'. 

 in 1920, the present author (KoiMAI, 20, a) published a preliminary 



