242 MARINE BIOLOGY OF THE SUDANESE RED SHA. 
AMATHIA. 
All the specific characters used so far depend upon the position of the 
zocecia or the size of some part of the colony. 
The zocecia are attached directly to the stem without any intermediary 
growth, and at the base of each zocecium there is a rosette plate ; the zocecia 
have a gizzard and 8-10 tentacles; there is no rhizome ; and the zocecia are 
connate nearly the whole length, whereas in Zoobotryon and other genera ot 
the Vesicularina they are free or partly so. The zocecia are biserial, the series 
in some species forming a straight row along one side of the stem, in others 
forming more or less of a spiral, and the series may continue the whole length 
of the stem or may only cover a small portion near the bifurcation. The 
branches usually dichotomize, or there may be a main stem from which 
branches arise as in A. plumosa, MacG., while in A. Wilsoni, Kirkp., there 
are three branches at a node. 
In some cases the terminal branches extend beyond the group of zocecia, 
gradually diminishing in size, being divided by one or more dissepiments, the 
position of which furnishes useful classificatory characters. The spiral is usually 
definitely in one direction right or left in a species ; but this is not universally 
the case—for example, in A. convoluta, Lamx., there may be a right curve in 
the older, and a left in the younger parts of the same colony. 
In the present investigation I Found that in A. semiconvoluta there is a light 
oval mark at the proximal end of each node (PI. 24. fig. 6), and a radicle to a 
few of the stems explained the meaning. 
A similar light mark oceurs in A. brasiliensis, Busk, and Busk mentioned 
the rooting of his A. tortwosa=convoluta ; also radicles occur in A. obliqua. 
The partial or complete formation of a radicle chamber to each zocecium or 
at regular intervals, even although few radicles may be formed, occurs in 
many species of Bryozoa. 
In the northern hemisphere the only form with a straight row of zocecia 1s 
the cosmopolitan 4. lendigera, L., whereas in Australia this group is well 
represented by nine species ; on the other hand, the group with the spiral 
series of zocecia is well represented in the northern hemisphere. So far as }am 
aware, no Amathia has yet been found in the Arctic or Antarctic. Although 
we must not arrange classification according to geographical distribution, yet 
it may often be examined to give a check to the correctness of classification”. 
* The following table shows the distribution of the species, so far as can be judged from 
the descriptions. Species occurring in more than one region are printed in small 
capitals :— 
Atlantic :—A. pistans, Busk ; A. Vipovicr, Hell. [the ‘Challenger’ specimens named 
A, lendigeru are A. Vidovici, Hell., and in several other cases Busk does not seem to have 
recognised the difference]; A. LENDIGERA, L. 
British and neighbouring seas :—A. LENDIGERA, L, 
