824 THE AMERICAN NATURALIST. [VoL. XXXIV. 
in type at different seasons of the year. In the summer, when the 
sexual products of the latter are at a minimum of maturity, the 
hybrids show a greater resemblance to pure Sphzrechinus plutei 
than do those obtained in the spring. Co A X. 
Protozoan Studies. — The continuation of Dr. Prowazek's! work 
upon the Protozoa contains his observations on many species and 
discussions of many protozoan problems for whose solution the frag- 
mentary evidence offered, though important in its bearings, is often 
insufficient. The reproduction of the Rhizopoda is illustrated by 
stages in the copulation of Euglypha and Trinema, and by sporula- 
tion in the autumn months in the same genera and also in Nebela, 
though no relation between the two processes was detected. These 
genera are frequently parasitized by Achromatium oxaliferum, and in 
this condition superficially resemble stages in sporulation. Autotomy 
was observed in Amceba and in Nebela, the rejected portion of the 
body usually containing the detritus from food vacuoles. From 
many observations on different species the author concludes that the 
formation of pseudopodia is always initiated by the ectoplasm. The 
structure and movements of flagella and of cilia are discussed and 
the inclusions in protoplasm are described and classified. Six types 
of non-living inclusions are recognized: (a) the Microgranula, com- 
posed of minute particles, the products of metabolism, found princi- 
pally near the vacuoles and the ectoplasm; (4) the Hyalogranula, 
derived from the first and composed of transparent, bluish-green, 
somewhat refractive, elongate or flattened granules which are abun- 
dant near the vacuoles in the endoplasm and are also frequently 
found on cysts and in gametes ; (A the Lamprogranula, consisting 
of yellowish or greenish, spherical or oval, highly refractive bodies 
apparently enclosed in vacuoles and usually exhibiting Brownian 
movements ; (7) excretory inclusions of spherical form, often with 
concentric structure and central cavity ; (e) excretory crystals of vari- 
ous types ; (f) the Leucogranula, composed of colorless, slightly re- 
fractive granules in the ectoplasm of Stentor and some other ciliates. 
A sessile heliozoan of unique form and habitus, Myxodiscus cr, stal- 
ligera, is described from a marine aquarium. Sessile life has induced 
a polar differentiation, the pseudopodia being confined to the free 
surface. Its food consists of ciliates. Phacodinium muscorum, @ 
new ciliate, is described from damp woodland moss. C. A. K. 
1 Prowazek, S. Protozoenstudien, II, Arb. zool. Inst. Wien, Bd. xii (1900); 
58 pp., 2 pls. 
