SPECIAL MORPHOLOGY. 21 



The second order, or the Cori/nidce, have the hydrosoma developed into a ccEnosarc of 

 very various forms, supporting many polypites without thecee, upon which are arranged 

 in circlets, or irregularly, many filiform tentacuUi. The ectoderm of the coenosarc (always ?) 

 developes a strong cuticle. The reproductive organs are produced by budding from the 

 bases of the polypites, or from the coenosarc, or from special (jonohlaHiidia, but they present 

 every variety in structure. The hydrosoma is fixed by a hydrorhiza. 



The Sertulariadce, which form the third order, have a coenosarc, with a strong, chitinous 

 cuticular layer, which is usually branched, and supports polypites enveloped in thecae. 

 Each polypite supports a subapical circlet of filiform tentacula. The reproductive organs 

 vary in structure, but are always developed either from the coenosarc or from gonoblastidia. 

 The hydrosoma is fixed by a hydrorhiza. 



The fourth order, or the Cali/coplLoridcE, have an unbranched coenosarc, which is flexible 

 and contractile, and has no hard, chitinous cuticular layer. The hydrosoma is free, and is 

 propelled by nectocalyces attached to its proximal end. The polypites have only one 

 tentacle, developed near their basal or proximal ends, and provided with lateral branches 

 ending in saccular enlargements. They have no thecae, but are sometimes enveloped in 

 hydroph3'llia. The reproductive organs are always medusiform gonophores, produced by 

 budding from the peduncles of the polypites. 



The fifth order contains the Pht/sophoridce, which have an unbranched or very slightly 

 branched, flexible, and contractile coenosarc, which has no hard, chitinous outer layer. The 

 hydrosoma is free, and its proximal end is modified into a pneumatocyst. It may be 

 propelled by nectocalyces or not. The polypites have either a single basal tentacle, or the 

 tentacles, whose structure varies greatly, arise directly from the coenosarc. There are no 

 thecse. Hydrophyllia are commonly, but not always, developed from the peduncles of the 

 polypites, or from the coenosarc. The reproductive organs vary, but are never simple 

 sacs. They are developed upon gonoblastidia. 



The Lucernariadtv, which constitute the sixth order, have the base of their hydrosoma 

 developed either primitively, or in the medusiform zooids to which they may, by a process of 

 fission, give rise, into an umbrella. The coenosarc has no chitinous cuticle. The tentacles are 

 simple, and are developed from the umbrella or its representative. There are no nectocalyces 

 or hydrophyllia. The reproductive organs are developed in the wall of the umbrella of 

 the primitive polypite, or in that of the medusiform zooids produced from it. 



Finally, I have retained the term Medusida as, at any rate, a temporary denomination 

 for all those members of the group termed Cryptocarpm by Eschscholz, GymnopUhahnatu 

 by Forbes, Craspedota by Gegenbaur, with whose origin we are unacquainted. It is not 

 yet proved^ that any of them are developed directly from the eggs of similar organisms, 

 and until this is the case the order can be regarded only as a provisional one. 



Using the term in this sense, the Medusida have a hydrosoma consisting of a single 



^ In using this expression, I by no means wish to question the great probability of the suppo- 

 sition that those ciHated embryos, which were observed by Miiller ('Miiller's Arcbiv,' 1851) and 

 Gegenbaur (' Zur Lehre vom Generations-wechsel,' 1854) to pass directly in the " Medusae " (Eginopsis 

 mediterranea and Trachynema ciliahim, proceeded from tlie eggs of similar Medusae. But, I repeat, 

 there is no proof of the fact. 



