ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
215 
of tlie second order consequent on an irritation diffusing itself strongly 
in the condensed nervous system. This irritation is caused by the 
strong stimulation of any point of that system which produces retraction, 
or by the stimulation of the diffused system which is transmitted to the 
ventral nervous system. The phenomena of extension of the tentacles 
does not necessarily depend on the ganglia, although the ganglionic 
influence has a marked action on the propagation of this reflex action, 
which is always centrifugal. The reacting power of a normal Asterias 
depends on the functional integrity of the diffused system, for it gives 
the power of reaction to the condensed system, and it is the first cause of 
that automotor power, which is the principal function of the condensed 
nervous system. 
The diffused nervous system is the seat of perception and sensa- 
tion, and keeps the animal in a state of activity, but it must not be 
forgotten that the relations between it and the condensed system are 
exceedingly close. 
The results of experiments with a number of poisons and with heat 
are given in the final part of the memoir. 
Notes on Echinoderm Histology.* — Mr. H. E. Durham, on the 
present occasion, confines his remarks to structures on which his obser- 
vations do not tally with those of other histologists. He first gives an 
account of the “ dorsal organ ” of Starfishes ; examined with a low power 
in the living state it has a lobulated appearance, and is seen to consist 
of a number of strands of tissue upon which may be transparent swel- 
lings of various sizes. Under a high power longitudinal fibrils may bo 
detected as well as large numbers of cells similar to the leucocytes seen 
in the coelomic fluid ; there are but few cilia on the surface of the organ. 
The functions of the haemal system appear to be (1) The distribution in 
a state of solution to the various organs of nutrient substances absorbed 
from the gut ; (2) The distribution of nutrient substances by means of 
amoeboid cells which use the strands of the system, as it were, like rail- 
way lines ; (3) It is the site for the production of amoeboid corpuscles; 
(4) It has some concern with the working up of effete material. 
Suggested Terms in Crinoid Morphology.f — We can only call 
attention to a number of new terms suggested for the use of the student 
of Crinoids which Mr. F. A. Bather has proposed ; the chief objects in 
view have been to give the same name to homologous parts, and to 
insure that parts which are serially homologous should receive names 
of a similar nature. 
Coelenterata. 
Morphology of Actinozoa.f — In the present memoir Prof. J. Play- 
fair M‘Murrich deals with the development of the Hexactiniae. He 
commences with an account of the segmentation of the egg and formation 
of the germ-layers in Metridium ; he finds that in all known cases the 
endoderm of the Actinozoa is formed by delamination, but this result 
only leads to tbe further question — was delamination the primitive 
* Quart. .Tourn. Mior. Sei., xxxiii. (1891) pp. 104-16. 
+ Ann. and Mag. Nat. Hist,., ix. (1892) pp. 51 66. 
J Jouru. of Morphology, iv. (1891) pp. 303-30 (1 ph). 
