100 
Annals of the Tkansvaal Museum. 
By placing this blind amphipod in the genus Eucrangonyx , I fear it 
may be interpreted that its origin has been largely implied by so doing. 
The suggestion that this is merely a case of the direct spreading of a cave 
form from Europe may possibly appear plausible as an explanation ; but 
if we examine the question from this point of view, we quickly discover 
that the explanation is not as simple as it may seem at first. I am 
unaware that any fluviatile gammarid has been recorded from tropical 
Africa ; if none exist there, then we must presuppose that some agent 
imported this cave gammarid from Europe ; the transportation may have 
been effected slowly and gradually or in one or two journeys. Mr. Hewitt 
has suggested to me that either birds or bats might possibly have been 
the agents in question. However, in a letter a little later than this 
communication he wrote that he considered it difficult to see how 
gammarids could be carried by bats and birds, since these Crustacea have 
no resting eggs. Mr. E. C. Chubb, of the Durban Museum, was kind 
enough to give me an answer concerning the likelihood of bats being the 
means of dispersing this amphipod, which, together with great numbers 
of bats, was found to be about the only occupant of the caves visited. 
He thinks that it is highly improbable that bats are influential in the 
spread of cave-dwelling Crustacea ; because ( a ) “ the cave-dwelling bats 
are not migratory, and on the contrary are very restricted in their range ”. 
This, however, would not necessarily apply if these bats originated from 
Europe, thus to have facilitated the gradual dispersal of cave Crustacea. 
( b ) “ They never settle on the ground, so it is inconceivable that they 
could come into contact with mud, containing eggs of crustaceans, as is 
possible with birds.” But the remark above about resting eggs may be 
recalled to memory, (c) “ They do not, as a rule, feed or drink in the 
caves in which they sleep. They feed on the wing in the open at dusk, 
or during the night. ... I should imagine they drink when 
skimming over the surface of the pools and streams in the open.” This 
communication was given in reference to the Microchiroptera or 
insectivorous bats. 
To say, therefore, that we see here a direct spreading of cave forms is 
not by any means the easiest way out of the difficulty. 
Now, if we suppose that the ancestor of the Gammarus-Crangonyx 
group was widely distributed in the temperate fresh waters of the world, 
say, about the middle tertiary period or even somewhat earlier, would it 
be anything out of the way to find living at the present time a 
representative, a survival, of that crustacean stock in South Africa, 
showing relationship to forms living in other parts of the southern 
hemisphere ? It is true that it has also near relatives in the northern 
hemisphere, to which it appears to be more closely allied ; but might not 
this be largely a matter of convergence owing to a similar mode of life, 
and the remaining factor of resemblance due to the great similarity 
existing between members of this group, a factor which would place this 
South African amphipod no nearer the European than the American and 
Australian forms ? 
Further, owing to the structure of the telson there seems to be little 
doubt but that Eucrangonyx robertsi possesses a somewhat primitive or 
generalized organization within the Gammarus-C rang onyx group. 
Therefore, in case the name of this animal may appear to be misleading, 
let it be clearly understood that no closer connection to the species 
Eucrangonyx vejdovskyi is implied than that, within the limits of this 
gammarid group, only little departure from the theoretically generalized 
