28 Dr. Reid 07i the Development of the Medusae. 
these animals *, where he describes four canals, — one in each 
angle of the extensible membrane surrounding the mouth and 
forming the lips, — passing from the circular canal already men- 
tioned, and also another circular canal placed in the free margin 
of the lips, I repeated my examinations ; and though I used 
glasses of very different magnifying powers, and made numerous 
trials, I could not satisfy myself of the existence of these canals. 
No doubt four equidistant white lines presenting the appearance 
of canals are seen, in certain conditions of the extensible lips, 
running in the positions indicated by Steenstrup ; but in some of 
the numerous forms which the lips assume these lines entirely 
disappear, and when present they seem to be formed by narrow 
ridges on the external surface, resulting from the quadrangular 
shape assumed by the lips. The free margin of the lips fre- 
quently presented indications of the presence of a canal, but I 
could never satisfy myself of its actual existence. In making 
such investigations, it must be kept in mind, that the internal is 
readily separated by pressure from the external layer, otherwise 
we may be led into error. In the almost daily examinations I 
have made of these animals during the last two years, I never 
observed the slightest traces of the hollow quadrangular body 
described by Steenstrup as growing from the lower surface of 
the cavity or stomach in the body of the animal, sometimes pro- 
jecting as high as the mouth, and placed in the middle of the 
stomach, like the clapper in a bell. 
The inner surface of the lips and of the stomach, and the ex- 
ternal surface of the tentacula and body, are covered with very fine 
cilia, so that currents of water, unless when the mouth is shut, 
are constantly passing in and out from the mouth and along the 
tentacula. The cilia upon the external surface of the body re - 
quire the use of the higher object-glasses for their detection, and 
for a long time they escaped my notice. 
The colony of larvae first obtained began to produce buds and 
stolons about the middle of January I8J6, and the other two colo- 
nies at the end of July of the same year. With intervals of com- 
parative repose they have gone on reproducing abundantly ever 
since ; so that, notwithstanding they are constantly suffering 
loss by death and other causes, the number of individuals in 
each colony has greatly increased. Whenever buds and stolons 
are formed, they commence by a thickening of the internal layer 
at those parts, causing a bulging outwards of the external layer. 
A single bud (fig. 10 a), occasionally two buds, grow from the 
upper surface of the stolon, and these become developed into 
larvse in the manner described by Sars. The buds form upon 
* On tlie Alternations of Generations, &c., translated for the Ray So- 
ciety, pp. 22, 23. 
