together with the Medusa produced from them. 357 



In connexion herewith the author has published the descrip- 

 tion of a new free-swimming Medusa found at Floroe, which so 

 much resembles some of the Medusa-buds produced by Cory- 

 morphce, 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 Steenstrup to be budded from Co- 

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

 laria;) : — 



Steenstrupia ylobosa, Sars, n. sp. 



Proles hydriformis ignota. 



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

 lino, margine anteriore oblique truncato, postice rotundato absque 

 appendice ; bulbis marginalibus quatuor, rubris, sequidistantibus, de 

 quorum uno prominente longe majore cirri marginales tres longis- 

 sirni, basi bulbosa connati, de cseteris tribus vero nulli, exeunt ; pro- 

 boscide cylindrica rubra, extra marginem pallii non porrecta, ore 

 simplici. 



Concluding Remarks. 



The nurse-genus Corymurpha possesses no small interest in 

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

 which the important physiological fact was ascertained (in 1835) 

 that the forms belonging to this group of animals are nothing 

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

 dusa?, and, indeed, of the lower Medusa? (Cryptocarpge, 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 squamatu, 

 Mull. (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 bv Wright 

 (Ediub. Phil. Journ. 1857, vol. vi. p. 79). 



