8 T. KOMAI : STUDIES ON TWO ABERRANT CTENOPHORES. 



coloured, excepting the }-el]owish-white spots mentioned above of C. 

 willeyi. C mitsiikurii (fig. 3) is generally light yellowish-brown, though 

 not always same in tone, this species showing the least colour variation. 

 Whether or to what extent an adaptive significance is involved in the 

 variabilit}' of the coloration, I can not say for certain, but it may be 

 mentioned as a fact that individuals of various coloration may occur 

 side by side amidst the same surroundings. But, there is an undeniable 

 tendency among individuals having similar coloration of occurring close 

 by. This, in my opinion, is due to division of the animal by accidental 

 damage and subsequent regeneration of lost parts. 



The three species show very close resemblance with one another 

 as regards both their external and internal features, and it is not neces- 

 sary to deal with the morphology of the three separately. The data 

 recorded in the present paper may be regarded to have reference alike 

 to all the species, unless special references are made to a particular 

 species. However, since C. ivilleyi and C. bocki are by far the commoner 

 species, these naturally have formed the chief material for my study. 



The animals, as tiiey adhere to the sea-weeds or to the alcyonacean 

 stock, might easily be mistaken b}' the unaccustomed eye for a planarian 

 or perhaps for a small nudibranch. When detached from the substratum 

 and placed in a jar with sea-water, they soon stretch out on the bottom 

 and assume a thin film-like appearance, in which condition they may 

 appear not unlike a kind of encrusting bryozoa or of compound ascidians. 

 The body in such an extended state may be said to be almost shapeless; 

 but when contracted, it is generally of an oblong outline. The size of 

 the animal varies considerably in different individuals and of course also 

 in different states of contraction of one and the same individual. Roughly 

 speaking, it generally measures 0.5-1 cm., more rarely 2 cm., in 

 diameter in a moderately contracted state, and 1.5-3 cm., sometimes 

 even as much as 5 or 6 cm. in diameter when fulK- extended. On the 

 whole, C. bocki is smaller than the other two species; it is commonlx' 

 1-1.5 cm., exceptionally 3 cm. in diameter in the fully extended state, 

 and may contract to a size of 0.5 cm. or somewhat less across. 



The dorsal surface of the body shows a small round unpigmented 

 area at the centre, indicative of the situation of the aboral sense-organ 

 as well as of the excretory pores (PI. i, fig. 4, s). On either side of 

 the sense-organ, along the longer median axis of the body, occurs a 

 tentacular apparatus (PI. 2, '^\<g. i, PI. i, figs. 3, 4), which constitutes one 

 of the most prominent organs of the animal. It consists of a basal part 



