722 
SUMMARY OF CURRENT RESEARCHES RELATING TO 
and to fixed animals. Hermaphroditism is completely retained by 
Ctenophores and Polyclads, and it is only in the higher forms that the 
Bilateria are seen to have the sexes separate. The Solenogastres are 
still partially hermaphrodito, and some of the larger groups of 
Molluscs and Annelids which have hermaphrodite glands appear to 
retain the primitive relations. The gonochorism of Cnidaria and of 
[Rotatoria is a secondary character, as, in the author’s judgment, is shown 
by the phylogenetic affinities of these animals. 
The author deals with his subject under the following heads : — 
(1) General Phylogenetic Laws ; (2) Development of Coelenterata 
from colonies of Flagellata ; (3) [Relation of Ctenophora to Sponges ; 
(4) of the same to the Cnidaria ; (5) Relation of Polyclads to Mollusca ; 
(6) Affinities of the Amphineura ; (7) Derivation of the Trochophore ; 
(8) On Substitution of organs. 
Tasmanian Mollusca.* — Mr. R. M. Johnston has published an 
introductory paper which he calls a provisional aid to the study of 
Tasmanian Mollusca. Something of the kind appears to be needed, for 
more than seven hundred species are known to exist in this area. 
y. Gastropoda- 
Development of Central Nervous System of Pulmonata.j — Dr. F. 
Schmidt gives an account of his observations on the development of the 
central nervous system in Limax agrestis and Clausilia laminata . He 
agrees with those of his predecessors who derive the entire central 
nervous system from the external epithelium ; the central ganglia arise 
from the epithelium of the sensory plates in the form of solid prolifera- 
tions ; soon after their separation from them the plates give off three 
blunt papillae on each side to form the foundations of the two tentacles 
and the oral lobes. The epithelium of three of the tentacles gives rise 
by proliferation to the tentacular ganglia. The two pedal ganglia 
appear at the same time as the central, and are derived from the epithe- 
lium of the foot-plate. The visceral ganglia do not appear till later ; 
they arise by proliferation of the epithelium in the neighbourhood of 
the orifice of the two primitive kidneys. 
At this stage of development the nervous system of the Pulmonata 
exhibits a remarkable agreement with that seen in such Lamellibranchs 
as Vnio or Cyclas. The subsequent changes in relative position may, 
Dr. Schmidt thinks, be thus explained : — After the several pairs of ganglia 
have separated in the embryo from the epithelium of the surface of the 
body and have become connected together by means of commissures, 
they form an integral system of organs, the further development of 
which proceeds quite independently of the increase in size and the 
unequal development of different parts of the body. Ganglia increase 
more rapidly in size than the commissures which unite them. 
Structures known as cerebral tubes arise from the sensory plates after 
the formation of the foundations of the central nervous system. They 
first arise as sac -shaped invaginations of the epithelium of the sensory 
* Papers and Proc. Roy. Soc. Tasmania, 1890 (1891) pp. 57-151. 
t SB. Nat. Ges. Univ. Dorpat, ix. (1891) pp. 277-82. See Ann. and Mag. Nat. 
Hist., viii. (1891) pp. 186-9. 
