BIOLOGY, GEOGRAPHICAL DISTRIBUTION. 
Tun. 5 
ment. He finds that the pericardium is formed by the concrescence of 
free mesenchyme cells. He finds that the common rudiment of the dorsal 
tube and the nerve ganglion is formed by free mesenchyme cells. No 
epicardium is present. In this respect Perophora differs greatly from 
Clavelina. 
From his investigations of Botryllus gouldii, Lefevre is able to corro- 
borate Hjort in his statement that all the important organs of the bud are 
ultimately of ectodermal origin. The ganglion is pinched off from the 
thickened ventral wall of the dorsal tube. 
Caullery considers that blastogenesis in Tuqicafa (and in general) has 
nothing to do with the theory of germ layers, which it neither supports 
nor demolishes, but that it is rather of the nature of a regeneration, 
and is especially an “ epigenetic ” process, i.e.^ it is an evolution 
dependent, above all, upon the conditions of environment. 
Hjort & Bonnevie give an account of the budding of Distaplia magni - 
larva, which brings that form into line with Botryllus and Polycliniim. 
They find that the nervous system and hypophysis develop from the inner, 
entodermal, vesicle. 
Driesch finds from his experiments on the development of isolated 
Ascidian blastomeres that, instead of forming fractions of embryos, they 
become entire embryos of reduced size. 
Korotneff discusses the formation of the germ layers in Salpa , and 
differs from Salensky and Brooks in his interpretation. 
Salensky, in continuing his work on the development of the Synas- 
cidice , treats of Didcmnum niveum and allied forms. He regards the 
Tunicata as Chordata , with only one pair of gill slits. He considers that 
tho curious condition iu Biplosoma is no case of metagenesis, but that 
the double larva is formed by division of a single embryo. 
Pizon has worked at the embryology of the simple Ascidians, Cynthia 
morus and A scidia villosa, chiefly at the nervous system and the peri- 
branchial cavities (of endodermal origin), and their prolongations, the 
epicardium. 
GEOGRAPHICAL DISTRIBUTION. 
Seeliger gives tables and a, full discussion of the distribution of the 
species of Pyrosoma in the Atlantic Ocean, both horizontally and verti- 
cally, and also as to the time of year when they flourish. 
Sluiter describes a number of species of Ascidiacea from the seas to 
the north of Australia. 
Caullery gives a list of the compound Ascidians of the coast round 
Boulogne. 
Ritter describes a new species of Goodsiria from the coast of Santa 
Barbara, California. 
