1883.] Recent Literature. 297 
however, he established for these strange beings a distinct sub- 
kingdom, the Mesozoa. It has been the general opinion, how- 
ever, that they are degraded Platyelminth worms. 
After an elaborate study of different species of this group, Pro- 
fessor Whitman considers their reproduction, embracing the phe- 
nomena of transition from the rhombogenic to the nematogenic 
condition, a comparison of the Dicyemidæ with the Orthonectidæ, 
and a general survey of their evolutionary cycle, so far as at present 
known. He then examines the development of the vermiform 
embryo, and the origin of the germ-cells, with remarks on endo- 
geous cell-formation. Finally he discusses the systematic affini- 
ties of the Dicyemids. Whitman sees “no reasons for doubting 
the general opinion that they are Platyhelminths degraded by para- 
sitism. Whether they and their allies, the Orthonectidæ, have de- 
ded from ancestors represented now by such forms as Dino- 
philus (Metschnikoff ), or from the Trematoda (Leuckart), is a ques- 
tion which further investigations must decide,” also remarking 
that “when we find an animal in the form of a simple sack, filled 
with reproductive elements, secured by position against enemies, 
supplied with food in abundance and combining parasitism with 
immobility, we have strong reasons for believing that the simplicity 
of its structure is more or less the result of the luxurious conditions 
of life which it enjoys, even if its development furnishes no posi- 
tive evidence of degeneration.” 
VERRILL’S CATALOGUE oF New ENGLAND MARINE Mottusks!— 
This is intended to include all the mollusca now known to inhabit 
England region that are not included in Binney’s edition 
of Gould's Invertebrata ‘of Massachusetts, published in 1870. The 
illustrations are noteworthy, not only from the beauty and evident 
accuracy of the drawings which have been made by Mr. Emerton, 
but from the perfection and cheapness of cost of the photo-litho- 
graphic work, 
BARRANDE’S SILURIAN AcEPHALoUs Moxiusks2—In a thick 
octavo volume with ten plates, M. Barrande has given the results 
of his exhaustive studies of the genera of Silurian Acephala of 
Bohemia, of the vertical distribution of the hore ~ ies, 
variations and the specific connections establis tween 
the Bohemian forms and those of other countries. 
Butteti OF THE AMERICAN Museum oF NATURAL History. 
—With the purchase of the Hall collection of New York fossils, 
and the accumulation or deposit of other material, and the ac- 
oes of working scientists to its force, the American Museum 
past gitlegue of Marine Mollusca added to the Fauna of New England during the 
Males Yay 2 P VERRILL. 
