400 Mtscellaneous, 



observed in other species of Echinida of among the Holothuriae, 

 Crinoidea, and Blastoidea I do not know ; our textbooks and 

 manuals give no information upon such questions. But, at any rate, 

 my specimens prove that the privilege of a variable number of para- 

 meres is not enjoyed by the Asterida alone. 



What conclusions are to be drawn from my discovery with regard 

 to the genealogical tree of the Echinodermata, is a question which I 

 only wish to raise here ; but my communication of it gives me the 

 opportunity of calling attention to the insecure foundation of the 

 above inference of Hackel's. 



With regard to the Medusae we are indebted to Hackel for the 

 demonstration of the original fundamental number of four, from 

 which the other fundamental numbers which occur among the 

 Medusae are to be derived ; and the question therefore presses itself 

 upon us whether the fundamental number five, which prevails among 

 the Echinodermata, is not also the original number. 



In my memoir upon Hydra (' Jenaische Zeitschrift,' 1880) I have 

 endeavoured to give an explanation of the original tetramerism of 

 the Medusae, which I may here confirm by an observation made 

 some years ago at Kiel. I must refer to the above-mentioned 

 memoir, the most essential results of which have also been obtained 

 by other naturalists, and have here only to indicate that the Medusa- 

 bud of Sarsia tubidosa is so placed with regard to the parent polyp 

 of Syncoryne Sarsii that one of the median planes of the young 

 Medusa fixed by the tentacles of the bud stands perpendicular to the 

 principal axis of the parent polyp, while the latter coincides with 

 the other median plane of the bud. 



The fundamental number of the quaternai'y Medusae, at least of 

 the Craspedota, is therefore causally conditioned by the lateral 

 budding of the Medusa on the polyp ; and it is therefore a question 

 whether something analogous cannot be demonstrated in the case of 

 the Echinodermata also, although in them there can of course be no 

 question of lateral budding. 



In any case the question whether pentamerism is or is not some- 

 thing primordial in the Echinodermata is still an open one ; with 

 reference to the undoubtedly original tetramerism of the Medusae 

 one might feel inclined to answer it affirmatively. — Zoohgischer 

 Avzeiger, no. 203, August 31, 1885, p. 505. 



