4 Tan. 
TUNICATA. 
Ascidians they are one-layered and epithelium-like; but in Pyrosoma 
they become oue-layered later on. The left coelomic sac increases greatly 
in size and forms a large cavity, while the right sac loses its cavity and 
forms a solid mass of cells which are afterwards dispersed through the 
body of the cyathozooid. The large left coelomic sac subdivides into two 
parts, a proximal axial part under the endostyle, which gives rise to 
muscles, elseoblast, reproductive organs, &c., and a distal' portion which 
becomes the pericardial tube and the heart. The chief conclusions are : — 
1. The ovum of Pyrosoma is meroblastic. 
2. The embryo (cyathozooid) is formed from both fertilized (blasto- 
rueres) and unfertilized (kalymocytes) elements. 
3. The blastomeres first divide into ectoderm and meso-endoderm, then 
the latter divides into multilaminar mesoderm and unilarninar endoderm. 
4. The mesoderm first appears in form of two typical coelomic sacs, of 
which one alone undergoes further development. 
5. The ectoderm forms the nerve ganglion, as a thickening, and two 
pericardial cavities, as invaginations, which grow forwards and back- 
wards, and later unite with the independent cloacal aperture. 
PHYSIOLOGY, METHODS, &c. 
Sluiter (13) describes seven out of the thirty-six species of Simple 
Ascidians he finds in the Java seas as living free in mud and able to 
move about. 
In his paper (7) on the methods used at the Naples Zoological Station 
for the preservation of marine animals, Lo Bianco devotes three pages 
to the Tunicata , and gives an account of the reagents and mode of treat- 
ment found to give the best results with the various genera. 
Laiiille (8) specially recommends for Compound Ascidians paralysing 
them when fully expanded in sea-water with chlorohydrate of cocaine, 
fixing with glacial acetic acid, and then preserving in various strengths of 
alcohol. He has some interesting observations and experiments on the 
alternation in the contraction of the heart and course of the circulation 
in living Tunicata. 
GEOGRAPHICAL DISTRIBUTION. 
Sluiter (13) describes thirty-six species of Simple Ascidians from the 
neighbourhood of Java. They belong to eight genera, and ten of the 
species are new to science. 
Herdman (7) discusses the distribution of the species of Ecteinascidia. 
Laiiille (8) gives information in regard to the geographical dis- 
tribution of the French Tunicata , and especially the Ascidian fauna of 
Banyuls-sur-Mer, where, besides many Simple and Compound Ascidians, 
the following pelagic forms are found : — Cyclosalpa pinnata } Salpa 
