184 SUMMARY OF CURRENT RESEARCHES RELATING TO 
polypide includes the digestive, nervous, and muscular organs. But the 
dual or polypo-cystid interpretation of the individual Bryozoite is 
rejected. 
Taking Flustrella hispida as a type of Gymnolaema, the author 
discusses the relations of the adult tissues to those of the larva. The 
walls of the oozoite consist of a cellular layer (“ endocyst ” of some), 
which secretes the chitinous eetocyst, and this layer arises directly from 
the larval ectoderm. Below it is a delicate parietal cellular layer, 
reflected around the invagination destined to form the orifice, and con- 
tinued down the gut to the funiculus. This is wholly derived from the 
larval mesoderm, and it gives rise to the muscles and gonads. It is 
simplest to call it the mesodermic tissue. As the endoderm of the larva 
disappears by histolysis, ectoderm and mesoderm form the whole of the 
adult, the former giving origin to the external sheath, the epithelium 
lining the gut, and the nervous system, the latter producing all the other 
structures. 
Prouho proceeds to describe Pherusa tubulosa , Alcyonidium varie- 
gatum sp. n., A. albidum , A. duplex sp. n., Membranipora pilosa , Hypo - 
phorella expansa. Important as his descriptions are, we shall restrict 
ourselves to summarizing what he has to say in regard to the develop- 
ment of the larva (of the Cyphonautes type), as observed in Membranipora 
pilosa , Alcyonidium albidum , and Hypophorella expansa. 
There is, however, an important discussion of the “ intertentacular 
organ,” the result of which must be noted. “ The intertentacular organ 
of Gymnolaema is a genital duct existing only in the sexual Bryo- 
zoites, never exhibiting the structure of a nephridium, but having the 
same position as the orifice of the metanephridium in Phylactolaema, 
and serving, secondarily, for the evacuation of the debris of the 
degenerated polypides.” 
The ovum, which is detached from the ovary into the general cavity 
of the body, is irregular in form, and exhibits sluggish amoeboid move- 
ments. Before fertilization and oviposition the ovum shows a very 
delicate vitelline membrane. Shortly after the egg is laid this membrane 
is separated off, and two polar bodies are extruded. In the three species 
above-named there is self-fertilization. Segmentation is equal and 
regular to the stage of sixteen blastomeres. Thereafter the primitive 
radial symmetry is changed for a bilateral arrangement. At the 32-cell 
stage four granular cells are invaginated or surrounded by the others, 
and form the beginning of the endoderm, but the gastrula is a sterro- 
gastrula without archenteric cavity. The region of the blastopore is 
soon closed. Soon thereafter two mesodermic cells appear, but their 
precise origin was not discovered. Then follows a series of modifica- 
tions which lead to the stage with an oral invagination and an excentric 
endodermic mass. The larval gut consists of an endodermic mesen- 
teron, a proctodaeum, and the oral invagination or stomodaeum. Prouho 
ventures the generalization that all ectoproctous Bryozoa with a free 
development have a larva of the Cyphonautes type. He compares this 
with the bivalved larva of Flustrella hispida , with the larva of Pedicel - 
b'na, and, incidentally, with a Pilidium. 
In a final chapter the author discusses some more general questions. 
(1) It is characteristic of Bryozoa that the ectoderm retains the power 
