,Q HYDROIDA 



gonophore of Corymorplia Sarsii is "fast immer" projecting from the nmbrellar cavity, while this is 

 "fast nie" the case with Coryiiiorpha vardocnsis^ is in the first place very vagne, and secondly depend- 

 ent partly on the varions contraction of the umbrella, parth- on the sex and the degree of maturity 

 of the gonophore. On the whole there can be no doubt that the description of Corymorplia vardOciisis 

 is based on an individual of Coryiiiorpha Sarsii. 



I have entered on this subject because Stechow (1912, 1913) puts together the species menti- 

 oned into a genus of their own, Avialthaca. The genus was first estabhshed by O. Schmidt (1854) for the 

 species Avialthaca uvifcra O. Schmidt, which is likely to be identical with Corymorpha Sarsii. It em- 

 braces the species of Coryviorpha whose gonophores develop into complete medusae, but, after all, not 

 breaking away, whereas the species whose medusae are normally breaking away, are gathered in the 

 o-enus more narrowly XxwnX.^A., Corymorpha. It is evident,however, that the medusa oi Aiiialfhaca excep- 

 tionally breaks away and then leads a wretched life, unfit as it is for free existence on account of 

 possessing a too small umbrella, the greater part of which is, into the bargain, occupied by the enormous 

 spadix with mature generative cells. The medusa strongly reduced, further, shows so near a rela- 

 tionship to the medusa of Coryiiiorpha nutans M. Sars that a systematist of medusae so skilful and 

 discerning as Hartlaub (1907) decides on only placing it in a subgenus of the medusoid genus 

 Corymorpha. The classification afterwards maintained by Mayer (1910), who distinguishes the two 

 groups of medusae as peculiar genera and even places them in quite different places in his syn- 

 opsis, as Amalthaca and Steciistrupia., only proves that he has failed to notice the excellent drawing 

 by M. Sars (1877), which shows us in fact, that the female gonophore, when fully developed, is often 

 an entirely typical Strciistrnpia., though one of the main tentacles is not quite so large as in Cory- 

 morpha nutans. The figures delineated by Sars wholly agree with the facts observed in living 

 individuals, and make good the correctness of Hartlaub's view of division, giving the right place 

 to affinity and biology. But where is then the fundamentum divisionis adaptable for the purpose of 

 classifying the CoryviorphaAWiQ. species of polyps into separate genera? 



From Amalthaca to Monocauhis glacialis there is, indeed, a very short step; all the difference, 

 as a matter of fact, is to be found in the gonophore, also here eumedusoid, being even somewhat more 

 reduced, as the tentacles, the special organs of the umbrellar margin, are entirely wanting. The con- 

 formity of the polyps is obvious; the gonophores of both species are eumedusoid and normally sessile; 

 the difference is accordingly too little for a separation of genera. 



Then only remains the group of Lampra., whose gonophores are cryptomedusoid. A generic 

 separation between, for instance, the species of Lampra and Corymorplia {Monocauhis) glacialis, will, 

 as I have recently pointed out (1915), correspond to a generic separation between c? and $ in Tubu- 

 lar ia indivisa Linne or Tubularia rcgalis Boeck. A particular argumentation of the unuaturalness 

 of this limitation is hardly required. But then it is obvious, as a matter of course, that a generic 

 separation of the species of Lampra and the other species of Corymorplia cannot be maintained. Also 

 the species of Lampra must be ranked within the genus Corymorpha. 



