No. 426.] NOTES AND LITERATURE. 499 
Much of the poor effect of the figures may be attributed to the 
author’s inclination to use ideal or diagrammatic representations. 
It is difficult to criticise fairly a work which, as the editor of the 
series says in a prefatory note, was written in 1897 and was entirely 
in proof in 1898. The epoch-making work of Looss on Trematoda 
and of Cohn and Liihe on Cestoidea, as well as many shorter con- 
tributions, have added so largely to our knowledge of these groups 
that what was thoroughly good in 1898 would now be strikingly out 
of date. One cannot help wondering how the work could have been 
held so long unpublished. In spite of these disadvantages, it will 
stand as a clear and well-balanced presentation of the subject, 
admirably arranged and suggestive in treatment. 
Henry B. WARD. 
Structure and Metamorphosis of Actinotrocha. — In the Journa? 
of the College of Science of the Imperial University of Tokyo, Japan, 
Ikeda! gives an account of studies on the development of Phoronis, 
from the unsegmented egg through the metamorphosis. For the 
earliest stages, the author was able to obtain living material in 
quantity, of the species Phoronis ijimai, while the structure of the 
larva was studied in four species (or forms) of Actinotrocha taken 
in the region of the Misaki Marine Biological Station. 
The author gives some interesting details as to the life history of 
Phoronis, showing that the adults probably die every year, the colo- 
nies being completely replaced by the metamorphosing larve. He 
criticises the present classification of the species of Phoronis, holding 
that several of the so-called species are not really distinct. 
A detailed account is given of the cleavage, gastrulation, formation 
and structure of the larva, and the transformation into the adult. 
Ikeda's results on some important or disputed points are as follows : 
The formation of the mesoblast begins at the beginning of gastrula- 
tion, by the irregular pushing of some of the entoblast cells into the 
cavity of the blastula. Mesoblast formation continues in the same 
manner from the two “anterior diverticula” of the archenteron, and 
from a ventral groove leading backward from the blastopore. The 
mesoblast cells are at first irregularly scattered, and only later arrange 
themselves to form the boundaries of the body cavities. The latter 
^ are thus not formed from enteric diverticula, as has sometimes been 

1 Ikeda, Iwaji. Observations on the Development, Structure, and Metamor- 
phosis of Actinotrocha, Journ. Coll. Sci. Imp. Univ. Tokyo, Japan, vol. xiii, 
Pp- 507-592, Pls. XXV-XXX. i 
