March 9, 1882] — 
But since the females have never been seen, it is pos- 
sible that they have a slightly different form and habit 
from that of the males, or possibly a very different form 
—perhaps hydroid! In either case the females may have 
existed in the deeper parts of the tank either floating or 
attached, and so have escaped observation, whilst the 
high-swimming males were taken in abundance. The 
eggs may have been fertilised in August by the dying 
males, and have proceeded to a certain stage of develop- 
ment in the autumn—being then normally arrested in 
development in the winter (the period corresponding to 
the emptying of the tank and to a period of drought in 
their natural condition), as in the case of Hydra viridis. 
Then they would be ready to enter upon a new period of 
development and growth in the following spring and early 
summer. 
4. The above suggestion is eminently hypothetical, and 
is somewhat difficult to reconcile with the result of the 
interesting experiment carried out at the suggestion of 
Mr. George Busk, F.R.S., in consequence of which some 
of the Medusee were transferred in 1881 from the Regent’s 
Park to the Victoria tank, in No. 1o house, at the Royal 
Gardens, Kew. This transfer was effected on June 16, 
four days after the second appearance of the Medusze at 
Regent’s Park. It is important to notice (as I am in- 
formed by Mr. Sowerby) that only six or eight full-grown 
Medusze were so transferred—and I cannot feel much 
doubt that these were all males—similar to all those 
whch I have examined. But with these half-dozen full- 
grown specimens, a quart of water containing many 
hundreds of very minute Medusz was also taken. The 
flisk of water and the little and big Medusze were poured 
out into the large tank at Kew on the same day—June 16. 
Nothing was seen of them at Kew until more than two 
months afterwards, when (on August 18) the whole tank 
was seen to be swarming with full-grown Liémnocodium. 
The question which arises is: Were these Medusz 
smply the young Medusze which had been transferred, 
now grown to maturity ; or were they a new generation? 
The chief objection to the view that the Medusz 
swarming at Kew in August were the same Medusz 
which were transferred in the young state from Regent's 
Park two months before, is found in the fact of their 
extraordinary abundance. I removed and examined 
myself at the end of September, from the tank at Kew, 
200 specimens. Other naturalists also obtained numerous 
specimens. In the meantime, be it remembered, the 
whole colony had died down or disappeared (as early as 
June 25) from the original tank in the Regent’s Park! 
Iam inclined to the view that the Kew Meduse were 
actually the same specimens as those transferred in the 
young state, which were placed in more favourable con- 
ditions at Kew than their fellows experienced in the 
Regent’s Park. The tank at Kew is larger than that in 
Regent’s Park, food is therefore more abundant, and 
moreover the temperature was, when I observed it, from 
six to ten degrees Fahrenheit lower in the tank at the 
former than in that at the latter locality (75°-80° Kew, as 
against 85°-90° Regent’s Park). 
A fact which is strongly against the supposition that 
the transferred Medusze had reproduced themselves is 
that the half-dozen mature specimens transferred were 
almost certainly males, and that the young specimens 
had not more than time to grow to full size, and were not 
observed to have arrived at maturity in the interval. 
I made renewed and careful examination of the Medusz 
at Kew at the end of September and in the beginning of 
October, when I had the advantage, through the kindness 
of Sir Joseph Hooker, of making use of the admirable 
laboratory recently erected in the Gardens. The speci- 
mens were often appreciably larger than any I had pre- 
viously obtained from Regenv’s Park (fully half an inch 
across the expanded disc). All the specimens examined 
(200 in number) proved to be males. At the end of 
NATURE 
445 
September there were no young or very small specimens 
in the Kew tank. In studying the genital pouches of 
specimens taken on September 27 I found below the 
ectoderm an abundance of ripe spermatozoa; these 
escaped through the wall of the pouch, which very readily 
ruptured. Below this layer of ripe spermatozoa, and 
between them and the ‘‘ structureless lamella”’ separating 
endoderm and ectoderm, I observed (as I had observed 
previously in specimens from Regent’s Park) a firm 
colourless tissue consisting of small nucleated cells. It 
occurred to me that these might possibly be ova, and the 
Medusz accordingly hermaphrodite. They had not the 
appearance of ova at this stage, but still I thought it 
possible that they were very -young ovarian cells. I[ 
treated specimens with osmic acid, alcohol, and picro- 
Carmine in succession, and cut sections of the genital 
pouches, with the result of satisfying myself that this 
dense tissue beneath the loose spermatozoa was of 
ovarian, but consisted simply of the mother-cells of the 
spermatozoa. 
I further tested this view of their nature by isolating a 
number of the Medusz in large glass jars which were kept 
in the lily-house at Kew. After a fortnight (October 8) 
the gonads or genital pouches had increased in length 
and bulk both in my isolated specimens, and in those 
swimming in the tank. On examination, the dense tissue 
underlying the spermatozoa was found to have disap- 
peared, or rather to have developed itself into additional 
crops of spermatozoids. Accordingly my hypothesis of 
hermaphroditism fell to the ground. 
It is, however, remarkable that even when half-grown 
the genital pouches of Zzmnocodium will emit ripe motile 
spermatozoids upon slight pressure, and that they con- 
tinue to form these bodies for so long a period of growth. 
Normally, I am inclined to believe, these spermatozoa are 
shed by rupture of the sac in incompletely grown indi- 
viduals, from time to time, whilst new crops are produced 
from the as yet unexhausted spermatic tissue. This 
would imply that somewhere in the tank there are eggs or 
females producing eggs which are to be fertilised by the 
very abundant spermatic particles. 
The tank at Kew was emptied and thoroughly cleaned 
out about the middle of October. The Medusa were 
still to be found, though they had much diminished in 
abundance. Some of the sweepings of the bottom of the 
tank were preserved with the intention of replacing the 
material in the tank, so that the eggs of the Meduse—if 
eggs there are—may have a chance of continuing the 
colony in the coming season. 
My object in publishing these notes is that they may 
be of service to others who may feel disposed to investi- 
gate Limnocodium, and to search for the females should 
opportunity again be afforded. I also hope that some 
suggestions may be offered by other naturalists, which 
will be of assistance in solving the problems presented. 
It is necessary to point out that the obvious plan of 
searching the sediment of either the tank at Kew or in 
the Regent’s Park for eggs is not feasible. The bulk of 
the material to be examined is too great, since these tanks 
have a square area of several hundred feet. There 
would be a better chance of finding the females (sup- 
posing them to be deep-living or sessile) in such a search 
than the eggs, were it possible to empty the tanks and 
get at the sediment when a suitable period for such 
search arrives. But, as a matter of course, the proper 
treatment of these tanks in connection with the cultiva- 
tion of plants cannot be interfered with. An obvious 
suggestion is that of isolating a number of both old and 
young Medusz in small tanks, and thus obtaining the 
means of knowing exactly what becomes of them and of 
anything they may produce. 1 have attempted this both in 
1880 and 1881, but without any success. The Medusa iso- 
lated, even in large bell-jars holding 5 or 6 gallons of water, 
and maintained at a temperature of 80° F., do not thrive. 
