28 Frot, 
PROTOZOA. 
Ceratium furcay {32) p. 195, figs. 1-3, 13-20. Tables showing variation 
in proportions of different individuals ; thus, in a series of 7 varieties, 
the distance from the end of the anterior horn to that of the left 
posterior one may vary from T45 to *3 mm., the distance between the 
ends of the two posterior horns from *037 to '079 mm., the breadth of 
the transverse groove from *031 to *057 mm. The stripes of the 
skeletal membrane consist of elongated thickenings of its outer wall ; the 
fine points are pores which penetrate the skeletal membrane ; the latter 
consists of an organic substance which shows the cellulose reaction with 
iodine, but is insoluble in ammoniate of copper ; the posterior horns may 
or may not bear small hooks outside and inside ; the protoplasm contains 
starch or some other amyloid substance, diatomin, and chlorophyll, hence 
is probably nourished like a plant. No contractile vacuole was observed. 
Ceratium tripoSy (32) p. 204, figs. 4-6, 21-27. A table shows very con- 
siderable variations in proportions to occur between different individuals, 
and that the stoutness of the body is inversely proportional to that of 
the horns. The species is connected with C. furca by varieties of both 
forms ; the chemical and histological proportions of the different parts 
agree with those of C. furca. 
Ceratium fusus, (32) p. 208, figs. 7, 8, 28-32. The relations to one 
another of the lengths of the two horns may vary from *253: '110 mm. 
to *088 : '264 mm., and the small right posterior horn may be either quite 
rudimentary or fully developed, even though small ; the protoplasm 
almost invariably contains a transparent vesicle filled with liquid. 
Ceratium coimutum, (32) p. 211, figs. 9-11, 33-35. A table of varia- 
tions in the proportions shows that, the right posterior horn may entirely 
disappear ; the skeletal membrane is divided up by a regular network of 
lines ; no pores have been found in it as in the three preceding species ; 
the membrane is frequently wanting over a large part of the surface. 
Ceratium hirucUnella^ (32) p. 215, fig. 12. In the structure of the 
skeletal membrane, it agrees with C. cornutum. 
Dinophysisy (32) p. 217 & 226, characterized. D. acutay p. 218, 
' figs. 49-62. Variation in proportions not great ; the chemical composition 
and the microscopic structure of the different parts agree in general with 
those of Ceratium (see above). 
Dinophysis michaelis ?, (32) p. 224, figs. 53 & 54. D. IceviSy p. 224, 
fig. 65 ; variation very slight. 
Peridiniumy (32) pp. 234 & 241, characterized. P. divergens, p. 234, 
figs. 39-46, includes depressum, Bailey. In structure and chemical pro- 
perties, the skeletal membrane closely resembles that of Frotoperidinium 
pellucidum, sp. n. (vide infra). The protoplasm contains numerous red 
fat-globules, and usually a transparent vesicle. The proportions show 
great variations in the different varieties. 
Peridinium tabulatum, (32) p. 239, figs. 37 & 38. The skeleton agrees 
essentially with that of P. divergenSy but the protoplasm contains diato- 
min, chlorophyll, and starch, and few or no fat-globules. 
Peridinium arcticumy Ehrb., P. longipeSy depressumy carolinianumy Bailey, 
referred by Maggi (35) to Ceratium. 
Glenodiniumy (32) pp. 246 & 251, characterized. G. cinctum, 1. c. 
