234 BULLETIN : MUSEUM OF COMPARATIVE ZOOLOGY. 



einige andere vor." The fact that chains were not found in the collec- 

 tions made at Kiel in the Baltic, but were found in the North Sea and 

 Atlantic, is possibly due to the times of the day at which collections 

 were made in the two regions. 



Lohmann unfortunately gives us no clue to the relative abundance of 

 the heteromorphic chains observed by him, but the inference one is led 

 to make from his discussion and conclusion is that they were not un- 

 common, perhaps were numerous. He figures but two chains, and these 

 only in outline sketches which are here reproduced in figures D (his 

 figure 21, II a) and E (his figure 21, III b) ; the first represents a chain 

 of two individuals, the posterior schizont being a normal Ceratium tripos 

 balticum Schiitt 1 and the anterior a Ceratium of different type called by 

 Lohmann C. tripos balticum forma lata. This anterior member is similar 

 in some particulars to the second cell (II 3 ) of the chain figured by me 

 on plates 1-3 and also to the cell (I 2 ) of the previous generation which 

 may be reconstructed from the skeletal parts A x and P 2 , the homologue 

 of the anterior cell in Lohmann's chain. 2 



Judging from the length of the apical horn, this chain is complete 

 anteriorly, possibly also posteriorly, though the antapical horns of the 

 posterior member of the chain are relatively short. In any event, 

 whether the two cells are sister schizonts or not, they are of different 

 types. The posterior is C. tripos balticum, belonging to the subgenus 

 Tripoceratium, and the anterior is G. minus, belonging to the subgenus 

 Biceratium, but still showing in the lateral deflection of its antapical 

 horns a slight tendency toward the Tripoceratium type of skeleton. 



1 Schiitt (1893, p. 70) applies this name to both the Baltic and Atlantic forms of 

 C. tripos, forms which Ostenfeld (1903) later separates as C. tripos var. subsalsa 

 (Baltic form) and C. tripos var. adantica, and Paulsen (1908) in his monograph of 

 the Peridiniales in Nordische Plankton follows the usage of Ostenfeld. 



2 A young Ceratium with undeveloped apical horn and very short diverging 

 antapicals which has many points of resemblance to Lohmann's f. lata was de- 

 scribed as Ceratium minus by Gourret (1883) from Marseilles. Another Ceratium 

 of somewhat similar form as regards the shape of the midbody, the shortness and 

 direction of the antapical horns, was figured by Bergh (1881), from Baltic waters as a 

 variety of C.furca. This form was designated later by Lemmermann (1899, p. 347) 

 as C.furca var. divert/ens. Lemmermann included in this variety Bergh's figures 

 14-17, but figure 17 is C. lineatum Ehrbg., and only figures 14-16 should be assigned 

 to a relationship to Lohmann's forma lata. The indications are that Bergh (1881), 

 Gourret (1883), and Lohmann (1908) were all dealing with the same form and that 

 Gourret's, the older name, should be used for it. There is also a possibility that 

 C. californiense is the tropical representative of this northern form. A more 

 extensive study of both northern and southern forms is needed for a final 

 settlement of the question. 



