108 THE VOYAGE OF H.M.S. CHALLENGER. 



strated that this monogastric Calyconecta is the detached free Eudoxia of a polygastric 

 Monophyid, which was first described in 1859 by Huxley as Sphaeronectes kollikeri 

 (9, p. 50). He called it Monophyes gracilis (compare below the descriptions of Genera 18 

 and 19). The peculiar metagenesis of these two forms of Calycophoridas was afterwards 

 accurately described by Chun (86, 87). 



A few Eudoxias of this genus were found by me in a bottle in the Challenger collec- 

 tion, taken in the Tropical Pacific, Station 274. Since the same bottle contained a 

 specimen of Sph&ronectes kollikeri, it is probable that they were detached from the 

 latter. I call them Diplophysa kollikeri. 



Diplophysa differs from all other Eudoxidse in the hemispherical, or nearly spherical, 

 form of its bract, and the simple ovate or cylindrical shape of its phyllocyst, which 

 ascends vertically in the axis of the bract. In the centre of the shallow subumbral 

 cavity of the bract is suspended a hemispherical gonophore, of about the same size, and 

 between these two, at the ventral face of the latter, is a simple siphon with its tentacle. 



Genus 11a. Eudoxella, 1 Haeckel, 1888. 



Eudoxella, Hkl., System der Siphonophoren, p. 32. 



Definition. — Eudoxidse with a mitriform, helmet-shaped, or hemispherical bract, the 

 exumbrella of which is smooth and without sharp edges. Phyllocyst with four radial 

 canals arising from its base. (Eudoxine of the genus Praya ?) 



The genus Eudoxella, as defined in my System, comprises free Eudoxias, the bract of 

 which is essentially identical with that of the sessile cormidia of Praya (PL XXXII. ). 

 I suspect, therefore, that this genus is the monogastric generation of a true polygastric 

 Praya. But the well-known species of this latter [Praya galea, Praya maxima, 

 Praya cymbiformis) are generally assumed to possess eudoxomes, which become mature 

 whilst still attached to the common stem. The question, however, whether this holds 

 good as a general rule, requires further accurate examination. 



A bottle in the Challenger collection, containing surface animals taken in the Tropical 

 Atlantic (Station 343, April 10, 1876), contained a few specimens of a Eudoxella, which 

 is very similar to the sessile eudoxome of Praya galea (PL XXXIL). But the helmet- 

 shaped bract was more highly vaulted, and the four radial canals, arising from the base 

 of the phyllocyst, were shorter and more equally disposed. The main difference was 

 indicated by the remarkable fact, that each Eudoxia exhibited no trace of the stem of a 

 Praya, and contained a large, completely mature gonophore. It is therefore probable 

 that this Eudoxia, which I call Eudoxella didyma, may be the detached cormidium of 

 some unknown species of Praya (Praya cymbiformis?), the gonophores of which are not 

 brought to maturity whilst sessile on the stem. 



1 Eudoxella = Sma.\l Eudoxia. 



