KOFOID AND SWEZY: UNARMORED DINOFLAGELLATA 419 



Comparisons. — The ocellus and dimensions separate this from P. ochrea 

 (fig. LL, 4). Its ocellus is of the same general form as that in Nematodinimn 

 partition (fig. NN, 4:), PoucJietia schuctti (tig. PP, 10), and Erythropsis lahrum, 

 (fig. SS, 6), indicating parallel lines of evolution of the ocellus in the four 

 genera, Protopsis, Nematodinium, Pouclietia, and Erythropsis. 



Syxonymy. — This species was originally described by Pouchet (1887) as 

 Gymnodinium polyphemus var. nigruvi and represented one of two varieties 

 into which he divided his G. polyphemus (1885^, pi. 26, figs. Ill, IV). Neither 

 variety, however, represents his original form in those characteristics which, 

 with fuller knowledge of these organisms, are now recognized as diagnostic, 

 and all three appear to be distinct species. The imperfections of Pouchet 's 

 figures and descriptions and his proljable inclusion of more tlian one form 

 vmder one name, as, for example, in his G. polyphemus (1885&), add to the 

 difficulties in subsequent specific identifications of these forms. The residts 

 are that later workers in this field, Schiitt (1895), Pavillard (1905), and Paul- 

 sen (1908), have added to the confusion and to the difficulties in synon^any. 



Pouchet's G. polyphemus var. nigrum, as originally figured (1887, pi. 10, 

 figs. 2-5), is distinctly ochraceous and possiljly has chromatophores, though 

 none are figured as distinct structures. In so far as indicated the sulcus is 

 longitudinal, midventral, and without torsion. The peripheral cytoplasm con- 

 tains everywhere finel,y divided black chromatin in the form of commas and 

 semicircles of irregular shape. These, however, are lacking in his figures 2 C 

 and 5 of an encysted form, in which also the eyespot is of a Avholly different 

 t}^)e. It is here simple with stout clavate lens and hemispherical melanosome, 

 whereas in the other figures the ocellus is compound with five to eight spherical 

 lenses and an amoeboid pigment mass. In view of the fact that the structure 

 of the ocellus is diagnostic in the group as a whole, and in our experience is not 

 subject to changes within the individual and species so great as here indicated 

 by Pouchet, we conclude that he has included in this species another without 

 peripheral pigment and with simple ocellus. Since its sulcus and girdle are in 

 no way indicated their allocation is impossible. We therefore exclude from 

 Protopsis nigra (Pouchet) his figures 2 C and 5 as indeterminate Pouchetiidae. 



Lemmermann (1899) allocates Pouchet's Gymnodinium polyphemus var. 

 nigrum to Pouehetia and advances it to spectific statiis, both of which changes 

 Schiitt (1895), the authority for the genus, omitted to make, probably because 

 of the fact that he made no revision of forms belonging to Pouehetia, rather 

 than by reason of the structural peculiarities of P. nigra. 



Pavillard's (1905) tentative inclusion of Schiitt's Pouehetia juno in the 

 synonymy of P. nigra appears to us wholly unwarranted Ity differences in 

 sulcus, girdle, ocellus, coloration, and dimensions. 



Paulsen (1908) makes the suggestion that Schiitt's Pouehetia rosea 

 (Pouchet), which is not Pouchet's species, may be P. nigra (Pouchet) Lemm. 

 As we indicate in our discussion of Schiitt's species whicli we regard as 



