DEPARTMENT OF MARINE BIOLOGY. I47 



Among other interesting Peridinea I found Blepharocysta splendor 

 maris and Ceratocorys (=Dinophysis) jourdani to be very plentiful. The 

 latter species is of special importance, as Dr. Cutzjun attempts to prove it to 

 be a connecting link between the two otherwise very different genera Phala- 

 croma and Ceratocorys. 



Entz has rather pointedly defined his understanding of it in naming it 

 Phalacroma ceratocorys, including herein both Phalacroma jotirdani and 

 Ceratocorys horrida; he considers it a Phalacroma that changes into a Cerat- 

 ocorys. In spite of the interesting observations and figures given by him, I 

 have always considered this to be rather incredible. 



The genus Phalacroma is a typical genus of the Dinophysidse, with a regu- 

 lar longitudinal division of the shell along a sagittal suture into two essen- 

 tially symmetrical halves (a right and a left one), while Ceratocorys belongs 

 to the Peridinidae, has no sagittal suture, and is obliquely divided into two 

 asymmetrical parts. After an examination of numerous specimens I came, 

 however, to the conclusion that Dinophysis jourdani — which Dr. Schiitt re- 

 ferred to the genus Phalacroma — is a genuine Ceratocorys, but a species 

 different from the common tropical C. horrida, although the species may be 

 easily mistaken for a Dinophysis or Phalacroma. The other larger species, 

 Ceratocorys horrida, was rare at the Tortugas, and when found was usually 

 far out toward the border of the Gulf Stream. I have not observed inter- 

 mediate forms between the two species. 



At the Tortugas I also met with a peculiar species of Peridinea, that has 

 been described and figured by Gourret under the name of Postprorocentrum 

 maximum. Gourret considered it to be related to Ehrenberg's genus Proro- 

 centrum, which it somewhat resembles. Later on, the same species seems 

 to have been described by Dr. Job. Schmidt, of Copenhagen, as Ostreopsis 

 siamensis. Dr. Schmidt also found most of the plates of the shell, showing 

 that it belongs to the Peridinidae, not to the Adinidse, such as Prorocentrum, 

 and is somewhat remotely related to the genus Gouyaulax. Like the species 

 of this latter genus, it also possesses numerous brownish yellow (diatomine- 

 colored) chromatophores. 



Occasionally I observed some specimens of Pyrocystis pseudonoctiluca, 

 especially toward the border of the Gulf Stream, but did not succeed in keep- 

 ing them alive sufficiently long to be able to discover whether it developed 

 from spherical to crescent-shaped cells. I also found a species, for which I 

 shall propose the name P. claparedei, for the Gymnodinium lunida of Schiitt 

 is a different warm-water species with a single larger gymnodinium in each 

 crescent-shaped cell. Such cells as the latter I observed at the Tortugas, but 

 only seldom, and it seems probable that they belong to Pyrocystis pseudo- 

 noctiluca as a stage of development. The other species of Pyrocystis oc- 

 curred only very rarely at the Tortugas. 



Further, I observed a most remarkable fact about a very widely distributed 

 organism, the systematic position of which has not yet been finally deter- 

 mined, viz, Spermatogonia antiqua. It is a protozoon with long, stout spines, 

 reminding one of those of radiolaria of the groups Acanthomctra; Cleve 

 therefore referred it to the radiolaria. The organism seems to be cosmo- 

 politan, occurring not only at Tortugas, but also off the coast of Norway. It 

 seems, however, to be more common in the warmer seas. It possesses a 

 nucleus or a similar body of a short, sausage-like shape and a peculiar, very 

 coarse structure. It differs from the radiolaria in possessing no central 

 capsule. To my great astonishment, I twice observed that living specimens 

 are able to move their spines suddenly and simultaneously toward one an- 



