i §4 
V. H. Blackman. 
are to he observed both around the nucleus and along the strands 
(fig. 10). The general colour of the protoplasm is the same as that of 
V. pseudonoctiluca, hut the form of the chromatophores I have not 
been able to make out. Nothing is known as to its reproduction. 
According to John Murray, this species is usually found in 
company with P. pseudonoctiluca, hut is not nearly so abundant. I 
have observed it in the Atlantic, as far north as 43" N. According 
to the same authority it is exactly similar in luminous power to the 
first described species. 
P. Lunula, Schiitt. 
Schiitt (9) in the first part of his studies on the Peridineae of 
the Hensen expedition, has given some good figures of this form 
under the name of Gymnodinium lunula, but as the description of 
the new species found during that expedition are held over for a 
second part, which has not yet appeared, no information, other than 
the explanation of plates, is supplied. Later, in Engler & Prantl’s 
“ Pflanzenfamilien,” Schiitt (10) removes this form from Gymncdi- 
nium, and places it in the genus, Pyrocystis, to which there seems little 
doubt that it belongs, for except for its curved shape, it agrees very 
closely with P. fusiformis. Schiitt also figures a few stages of 
flagellate spore formation in this species, which will be discussed 
later in relation to the question of the systematic position of the 
family. 
P. Hamulus, Cleve. 
Cleve (2) in 1900, figured in outline an organism which he 
doubtfully placed in the genus Pyrocystis, and to which he gave 
the above name. This species has been familiar to me since 1898, 
and there can be little doubt that it is a true Pyrocystis. It is the 
form which appears in 1899, in the list attached to a paper on Atlantic 
Peridineae, by Murray and Whitting, as Pyrocystis bicornis, 
Blackmn (see synopsis). As this was a mere nomen nudum, 
without figure or description, it must give way to the later name of 
Cleve, to which a figure was attached, though no description. The 
general form is well shown in Figs. 5 and 6 ; the body is irregularly 
ovoid, and is prolonged into two long, stout, tapering and curved 
horns. The nucleus lies in the centre of the body, and the protoplasm 
clearly extends into the horns, though the material under observation 
was not sufficiently well-fixed to enable one to determine its exact 
arrangement. The average length of the body is about 80 /i, and 
that of the horns about 250/z. This species has been observed in 
the Indian Ocean and in the Atlantic, Cleve (3), where it ranges up 
to 37° N. 
