D. Keilin 
155 
So far, the characters of this gregarine agree with all we know of the general 
structure of the group. The peculiar character of the species is confined to the 
structure of its cyst. It is well known that in gregarines two full-growy sporonts 
(or gametocytes), when associated for reproduction, contract their body and 
form a more or less spherical mass which is surrounded by a common cyst. 
In the case of Allanlocystis dasyhelei, on the contrary, the two sporonts 
associated for reproduction, without changing their form, secrete a very 
elongated sausage-like cyst 1 , measuring 140-150 a in length and only 20 a 
in width (PI. X, fig. 4). 
Once the cyst is formed, the protoplasm slightly retracts, the septum which 
previously separated the two gametocytes disappears, and the interior of 
the cyst forms a fused mass consisting of dark granular protoplasm with 
irregular contours. The gametes and the sporoblasts seem to be formed by 
the ordinary process common to almost all gregarines. In a few cases I could 
follow in vitro the formation of the sporoblasts; a freshly formed cyst (similar 
to that represented in PL X, fig. 4) left in normal salt solution at 7.15 p.m. 
one day, was found at 10 o’clock the next morning with completely formed 
sporoblasts as represented in PL X, fig. 5. 
The sporocysts (PL X, figs. 6 and 7) are spindle-shaped, with one side 
slightly more prominent than the other; they are 18 p long and 6*5 p wide. 
It is important to note here that the only gregarine known, where sporonts 
do not contract their body before sporulation, is the very interesting form 
found by Leger (1892, pp. 159-160) in the coelom of the Polychaete worm 
Glycera, and described by him under the name Ceratospora mirabiles Leger. 
This gregarine, however, differs from Allantocystis and all other known 
gregarines in a very important character, namely, the associated sporonts 
remain always separated from each other by a septum, and the gametes of 
each sporont develop parthenogenetically into spores. It would be of great 
interest to study cytologically the development of these spores, but un¬ 
fortunately, as Leger mentioned, this gregarine is rare. The peculiar shape of 
the cysts of Allantocystis makes it difficult to define the systematic position 
of this genus. 
DENDRORHYNCHUS SYSTENI n.g., n.sp. 
This gregarine was found in a larva of a Dolichopodid fly: Systenus sp., 
probably Systenus scholtzii Loew 2 , which occurs with the larva of Dasyhelea 
obscura Winn, in the decomposed sap of the Elm tree; but, while the latter 
larva is saprophagous and feeds upon decomposed sap, the larvae of Systenus 
1 Whence the generic name Allantocystis. 
2 The host was kindly identified by Mr C. G. Lamb as belonging to the genus Systenus being 
probably S. scholtzii Loew, but for the exact identification of the species it is important to examine 
the which unfortunately I failed to obtain. The $ of this species is difficult to distinguish 
from that of S. adpropinquans Loew whose larvae were found by Laboulbene (1873) in the sap of 
the Elm tree. 
