together with the Medusa produced from tuetn. 357 



lu connexion herewith the author has published the descrip- 

 tion of a neiv tree-swimming Medusa found at Floroe, which so 

 much resembles some of the Medusa-buds produced by Cori/- 

 morpha, that he thinks it probably originates from a species of 

 this nurse-genus. It belongs to Forbes's genus Steenstrupia, 

 differing in the following characters from the four known spe- 

 cies {S. rubra, Forbes, /S. flaveola, Forbes, S. lineata, Leuck., 

 and the species observed by Steeustrup to be budded from Co- 

 ry ne fritillaria, which may be indicated by the name of S.fritil- 

 laria) : — 



Steenstrupia globosa, Sars, n. sp. 



Proles hydriformis ignota. 



Proles medusiformis |^-pollicaris, pallio globoso-campanulato, hya- 

 liiio, margine auteriore oblique truucato, postice rotundato absque 

 appendice ; bulbis margiualibus quatuor, rubris, sequidistantibus, de 

 quorum uuo prominente longe majore cirri marginales tres lougis- 

 simi, basi bulbosa conuati, de caeteris tribus vero nulli, exeuut ; pro- 

 boscide cylindrica rubra, extra marginem pallii non porrecta, ore 

 simphci. 



Concluding Remarks. 



The nurse-genus Corymorpha possesses no small interest in 

 several respects. It was one of the first Hydroid polypes in 

 which the important physiological fact was ascertained (in 1 835) 

 that the forms belonging to this group of animals are nothing 

 more than a preliminary generation or so-called nurses of Me- 

 dusse, and, indeed, of the lower Medusae (Cryptocarpse, Eschsch. ; 

 Gymnophthalmata, Forbes; Craspedota, Gegenb.), which are 

 consequently developed by the process of the alternation of ge- 

 nerations. 



They are further distinguished by their colossal size in com- 

 parison with all the other known Hydroida, as also by their 

 always occurring as single or solitary individuals, never com- 

 pound, or with several individuals united to form a colony. The 

 formation of colonies appears otherwise to be the rule amongst 

 the Hydroida : all known genera and species, even those which 

 were long regarded as simple, have been found by recent inves- 

 tigations to be proliferous, and therefore forming colonies*. 



The only known permanently solitary Hydroida (and therefore 

 never proliferous or forming colonies) are the two genera Cory- 

 morpha and Myriothela established by me (Reise i Lof. og Finm. 

 p. 134, and described in detail in ' Forhandl. ved de skand. 



* Many years ago I ascertained that our common Coryne squa.natu, 

 Miill. {Clava multicornis, Forsk.). which was previously described as a 

 simple animal, was proliferous at its base, and consequently formed colo- 

 nies, — an observation which has also been recently confirmed by Wright 

 (Edinb. PhU. Journ. 1857, vol. vi. p. 79). 



