DIMORPHISM IN TTYCHODERA CAPENSIS. 393 
A Form of Dimorpliism and Asexual Reproduction in Ptycliodera capensis 
(Hemichordata). By J. D. F. Gilchrist, M.A., D.Sc, F.L.S., 
Professor of Zoology in the University of Cape Town. 
(With 7 Text-figures.) 
[Read 7tli June, 192.3.] 
The Hemichordata, considered as including the three groups represented 
by Cephalodisciis, Balanoglossus, and Plioronis, are of such importance as 
possible connecting links between the great groups of Vertebrates and Inver- 
tebrates that any new facts bearing on their relationship to each other or 
to other phjda of the animal kingdom are of particular importance. The 
following observations on a species of Balanoglossid, which exhibits a form 
of dimorphism, associated with sexual and asexual reproduction, may there- 
fore be of special interest. 
There appear to be at least four different species of " Balanoglossus " in 
S. Africa: three, which I have already described (Trans. Phil. Soc. S. A£r. 
vol. xvii. pt. 2, p. 151, 1908, and Ann. S. African Museum, vol. vi. pt. 2, 
p. 207, 1908), Ptycliodera capensis, P. proliferans, P. natalensis, and an 
undescribed species, of which only a single imperfect specimen has as yet 
been found. The first and second were found in a tidal sandy pool in False 
Bay, the third in the muddy mangrove-bordered flats of Durban Bay, the 
fourth in a crevice of a rock at low-water mark in False Bay. The first two 
are obviously different from the third and from the fourth, which does not 
belong to the genus Ptychodera. The first two also seem to be quite distinct 
from each other, but their constant association in the same pool, their 
anatomical resemblance in all but the posterior regions of the body, and the 
fact that there is a normal process of asexual multiplication in one of them, 
gave rise to the suspicion that they might represent sexual and asexual 
forms of the same species. 
Both species belong to the genus Ptychodera, the Tauroglossus of Spengel, 
and there appears to be no specific difference in size, shape, or structure of 
the proboscis and collar region. The size, shape, colour, and position of the 
genital wings immediately behind the collar are also similar. The differences 
in the posterior part of the body are, however, well marked, for (1) in 
P. proliferans (fig. 2) there are no hepatic caeca, either external or 
internal ; (2) the caudal region is not clearly marked off from the branchio- 
genital region, and the bright yellow gonads seem to be continued into this 
region as two narrow streaks on either side of the intestine, which is never 
filled with sand as in P. capensis ; (3) asexual reproduction takes place by 
LINN. JOURN. ZOOLOGY, VOL. XXXV. 29 
