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The Schizogregarines 
(7) Genus Aggregata. 
The genus Aggregata was founded by Frenzel (1885) for Gre- 
garines infesting various Decapod Crustacea (e.g. Portunus arcuatus and 
Carcinus maenas ). These Gregarines in Crustacea had been seen by 
many of the earlier writers, e.g. by Cavolini (1787),Rudolphi (1819), and 
Diesing (1851). Frenzel considered that the coelomic cysts, really 
occurring in the peri-intestinal lymphoid tissue and projecting into the 
haemocoel of the crabs, belonged to the life-cycle of the Gregarines 
found in the lumen of the intestine of the same hosts, and that they 
arose from a conjugation. Labbe (1899) accepted Frenzel’s genus and 
united it with Porospora of the lobster under the Gregarina gymnosporea, 
since naked sporozoites (so-called) occurred, grouped around residual 
protoplasm. 
Geoffrey Smith (1905), however, showed that no conjugation occurred 
in the life-history of the “ coelomic ” Gregarine, Aggregata inachi, of 
Ivachus dorsettensis. He found that at the beginning of sporulation 
there was only a single nucleus which divided and gave rise to daughter 
nuclei at the periphery of the cyst. These nuclei, each surrounded 
by a small mass of protoplasm, became so-called sporozoites. The 
intestinal Gregarines of crabs and the coelomic cysts of Aggregata 
must, then, be separated, as has now been done by Leger and Duboscq. 
No resistant sporocysts are formed by Aggregata in the crab. 
Regarding the development of the sporozoites of Aggregata, Frenzel 
(1885) suggested the remarkable hypothesis that their further develop¬ 
ment might occur in Cephalopods, for which the crabs serve as food. 
This interesting forecast was found to be correct by Leger and Duboscq 
(1906), who demonstrated experimentally that the Aggregata of crabs 
and the Eucocddium of Cephalopods only represent different stages in 
the life-cycle of one parasite. In this connection it is interesting to 
note that the gastric juice of Sepia is without action on the sporocysts 
of Aggregata. From the researches of Moroff and Leger and Duboscq 
it is now considered that we have in the parasite in question a 
digenetic and hetero'ic Gregarine, whose schizogony occurs as “Aggre¬ 
gata” in the crab, and whose sporogony occurs as “ Eucocddium ” in 
the Cephalopod. 
Eucocddium was formerly unique among the Coccidia in possessing 
no schizogonous cycle, a sporogonic one only being known. The stages 
in the Cephalopods had been investigated by many well-known workers 
in the past, including Lieberkiihn (1854—5), Eberth (1862), Schneider 
