13 Gcal 
C(ELENTERATA. 
concretions analogous to those of the “ ears ” in the Craspedota ; in 
others {Aurelia), one or more eye-spots are also present, sometimes with 
lenses {Charyhdea, Nausithoe). It is not possible to give here more than 
a passing allusion to Claus’s paper on Charyhdea (8), of which type no 
species was examined by the Hertwigs. Bohm’s already cited paper (4) 
is especially noteworthy for its chapter on the gemmation in the Medusce. 
H^ckel's system (11) dividing iAiQ Medusce into two groups, Craspedotoe 
{Cryptocarpa, Qymnophihalma) imd. Acraspedce {Phanerocarpie, Steganoph- 
thalmce) and 8 ‘‘Orders” — Anthomedusce, Leptomedusoi, Trachymedu&ai, 
Narcomedasce, Scyphomedusce, Conomedasce, Peromedusce, and Discomedusce 
— into the characters of which the differences recorded above, and offered 
by the nervous system, sense organs, and organs of generation, and the 
relation to the two orders of Uydrozoa, enter largely — is the forerunner of 
a forthcoming systematic work on the Medu&oe. The special record of 
Haeckel’s system may therefore more conveniently be postponed until 
next year. 
The continued observations of Romanes (22) show that Medusae are very 
favourable objects for physiological experiments on, and investigations 
of, the nervous system, and that they show in the phenomena observed 
a remarkable agreement with higher animals. The genera experimented 
on are Aurelia, Sarsia, Staurophora, and Tiaropsis. The differences 
exhibited by the craspedote and acraspedote Medusae in the mode of 
action of the nervous system, &c., are in excellent accordance with 
the anatomical facts brought forward by the researches of late years. 
It is impossible here to give a statement of the multiplied and in- 
genious experiments (section, segmentation, heat, cold, light, gases, 
poisons, electricity, &c.), to which the author subjected his animals ; 
a few facts most intimately connected with their natural conditions 
of life may however be mentioned. The “ necto-calyces ” of Cras- 
pedota are paralysed by removing the margin, the umbell® of Acras- 
peda partly, by removing the marginal sense-bodies (the lithocysts), 
which are the exclusive seats of spontaneity, so far as the primary 
movements are concerned. Water below 20° Fahr. suspends irritability 
and spontaneity, while a temperature above 70° permanently makes the 
rhythm slower, after having temporarily quickened it ; after having been 
frozen solid, Aurelia will recover on being thawed. Oxygen accelerates 
the rhythm, while carbonic acid retards it and in strong doses destroys 
both spontaneity and irritability. Deficient aeration of the water will 
ultimately suspend spontaneity, but on restoring the animals to fresh sea- 
water their recovery is surprisingly sudden. Light acts as a powerful 
stimulus on Sarsia ; but after removal of its marginal bodies it no longer 
responds to a luminous stimulant. Poisons act on the Medusae in a 
manner strongly analogous to their actions in higher animals, with the 
exception that life is not destroyed till long after all signs of irritability 
are lost. The same is true of fresh water, which acts as a deadly 
poison, not however through the difference of density, as has been sup- 
posed ; naked-eyed species usually cease their movements the instant they 
touch the fresh water, but the covered-eyed species are slightly more 
tolerant of its influence. Sarsia never survives a stay of fifteen minutes 
