71/?^ Menon, Notes on Semper s Larvae. 407 



Notes on Semper's Larvae. By K. Ramunni Menon, B.A., 

 Christ's College ; Assistant Professor, Presidency College, Madras. 



[Received 3 March 1902.] 



While examining the Madras Plankton during the months of 

 September and October last I was fortunate enough to come 

 across some specimens of the Anthozoan larvae originally described 

 by Semper in 1867, and since then in greater detail by E. Van 

 Beneclen (1) As some of the stages obtained on the present 

 occasion have not, as far as I know, been previously described, and 

 further appear to me to be of some value in determining the 

 phylogenetic relations of the Zoantheae, the group to which these 

 larval forms undoubtedly belong, a few observations have been 

 embodied in the following notes. I regret I have not been able 

 to consult Van Beneden's recent volume on the Anthozoan larvae; 

 I cannot thus ascertain if any of these stages or observations are 

 really new. 



I must here express my most grateful thanks to Prof. A. G. 

 Bourne for enabling me to obtain a regular and abundant supply 

 of Plankton material ; and to Mr A. E. Shipley, of Christ's College, 

 for communicating these notes for publication. 



Of Semper's first larva — named Zoanthella, by Van Beneden — 

 I obtained half-a-dozen specimens of a very early stage, and after 

 a prolonged search succeeded in getting one of a much later stage. 

 This was carefully preserved and cut into sections. Of the young 

 specimens one was preserved and cut ; the others were kept in 

 sea-water with a view to obtain later stages. This attempt proved 

 a failure, as after a period of over a month the two which sur- 

 vived were only a little more advanced than the earliest stage. 



The single specimen of the latest stage obtained measured 

 nearly 8 mm. in length, and was about 3 mm. thick in the middle. 

 It has a pyriform body with a circular mouth placed at the narrow 

 anterior end (fig. 1); a small ventral lip projects forwards below 

 the mouth, but there is no dorsal lip. I have not seen the aboral 

 aperture mentioned by Semper, and do not believe any such exists 

 in this larva. The whole surface of the body is covered by small 

 cilia. The peculiar, iridescent, ventral, longitudinal band of long 

 cilia, stretching from near the mouth to about a quarter of the 

 animal's length from the aboral end, beats in a slow, rhythmical 

 manner from side to side and apparently plays only a subsidiary 



