Mr. W. Clark on the Animal of Kellia rubra. 143 
branchial currents is a sad mistake ; nothing can be more irre- 
gular, capricious, and uncertain ; they depend entirely on the 
volition, habits, and wants of the animal, and are often suspended 
for weeks in Kellia rubra, and twice in every twenty-four hours 
in the mussels and numerous Gasteropoda inhabiting the higher 
levels of the littoral zone. 
I positively dissent from Mr. Alder’s views, repeated in his 
last paper, that the open fold of Kellia rubra is a special bran- 
chial organ. That the water enters therein no one disputes, imas- 
much as this fold is a simple continuation of the ventral portion 
of the mantle, and the water must flow therein, as it does in 
every other part of an open mantle. This sentiment is a repe- 
tition of one in a former paper ; but it 1s necessary to keep it in 
view, to show that the fold in question has no pretensions, as I 
think, to be considered as a special branchial organ to supply the 
want of one in the usual place nature is always accustomed to 
fix it, and I am inclined to think that Mr. Alder will ultimately 
find that she has not, as he states, placed the “ inhalant siphon ” 
“ before instead of behind.” 
This idea of inverting the invariable order of nature to account 
for an anomaly in the structure of Kellia rubra is a stretch of 
imagination, far beyond my conjecture, that the fold in question 
may be to assist locomotion. But I shall not be surprised to find 
that Mr. Alder and myself have mistaken the use of this fold in 
Kellia rubra, and that it may minister to supply water to the 
viviparous colony deposited in the ovarium of the animal of this 
species, and also act as an oviduct and receptacle for the young, 
until they are sufficiently developed for exclusion. This idea 
arises from having seen, when examining some Kellia suborbicu- 
laris in a saucer, several testaceous young ejected from the ano- 
malous tube of one of the animals, which I find, as Mr. Alder 
states, 1s entire, and not an open fold as in Kedlia rubra ; these I 
immediately gathered up, and have them now by me. I men- 
tioned some time ago this circumstance to Professor Forbes ; 
but notwithstanding this fact, I have never been able to dis- 
cover, in any of the very numerous ovaria of this species I have 
examined, anything but ova, but it is exceedingly probable the 
shells I saw ejected may have been deposited in the curious and 
extraordinary appendage in this animal, and there received the 
development in which I found them. 
As to Mr. Alder’s other observations, on some quotations from 
my last paper, I leave them as I find them. I really have some 
difficulty in appreciating their scope, aim and applicability ; in- 
deed some of them are so involved as not to be clear. I therefore 
beg him to accept the following new demonstration of the fallacy 
of the inhalant and exhalant branchial currents in the bivalves 
