62 SUMMARY OF CURRENT RESEARCHES RELATING TO 
septation of the thallus like that of Codium, but, in the former genus, 
a considerable secondary thickening of the wall of the tube. These 
two genera are also distinguished from Codium by the power of regene- 
ration of detached portions of the thallus. 
Notwithstanding these biological differences, the author regards the 
CodiaceaB as forming a well-defined natural group. 
Caulerpa.* — Mdme. A. Weber Van Bosse gives a monograph of the 
family Caulerpeso, composed of the single genus Caulerpa , which she 
thus defines : — Green Algge with multinucleate thallus, unicellular, and 
traversed by anastomosing cords of cellulose ; propagation non-sexual, 
by detached fragments of the thallus ; spores unknown. The thallus 
is composed of a creeping tube (the stolon is very rarely wanting), 
which puts out rhizoids on its lower surface, and fronds on its upper 
surface; the fronds vary greatly in form, are usually ascending, but 
sometimes creeping, simple, but branched. The 53 species, some of 
them new, are arranged by the authoress in 12 sections. 
Pleodorina illinoisensis.f — Under this name Dr. C. A. Kofoid de- 
scribes a new species from plankton on the Illinois river, and gives the 
following diagnosis of the genus. Colony consists of a spherical or 
elliptical coenobe of greenish biflagellate cells of two types, vegetative 
and gonidial, in the anterior and posterior parts of the colony respec- 
tively, -which lie in the periphery of a hyaline gelatinous matrix, and 
are surrounded by a common hyaline envelope. Cells each with one 
reddish eye-spot, which is more prominent in the anterior part of the 
colony. No connecting filaments between the cells. Non-sexual pro- 
pagation by gonids. which are formed by increase in size of a part of 
the cells of the colony. Daughter-cells escape from the parent-cells 
as small colonies of biflagellate cells which at this stage are all similar. 
Sexual reproduction unknown. 
Chlamydomonadineae.J— M. P. A. Dangeard gives the following as 
the result of recent observations on this group of Algae, comprising the 
genera CMorogonium, PJiacotus, Carleria, and Clilamydomonas , which he 
regards as “ the principal pivot of the vegetable kingdom.” 
A distinct boundary can almost always be detected between the proto- 
plasm and the cliloroleucite. The single chloroleucite is sometimes 
traversed by protoplasmic trabecules. The protoplasm is homogeneous 
or granular, while the chloroleucite is alveolar. The structure of 
the nucleus varies much. The karyokinetic mode of division occurs 
in nearly all the genera ; the number of chromosomes is constant in 
the same species, but varies in the different species and genera. The 
process does not differ in any essential point from that in the higher 
plants. The number of chromosomes is the same in the ordinary 
sporanges and in the gametosporanges ; in the latter it remains con- 
stant during the successive bipartitions ; no reduction takes place before 
impregnation ; the probable time is the germination of the ovum. When 
the two gametes conjugate to form the ovum, the two nuclei present no 
appreciable difference in size or structure ; they are obviously attracted 
* Ann. Jard. Bot. Buitenzorg, xv. (1898) pp. 243-401 (15 pis.), 
t Bull. Illinois State Lab. Nat. Hist., v. (1898) pp. 273-93 (2 pis.), 
X Comptes Rendns, cxxvii. (1898) pp. 736-8. 
