H. Henry 
195 
infection with three distinct parasites. The young oval forms of 
Haemogregarina rovignensis are described as being derived from 
sporozoites which have penetrated the red blood corpuscles and which 
are destined to become schizonts. It is much more likely that the 
sporozoites penetrate the cells of some of the internal organs and that 
the oval forms found in the red corpuscles are the resulting merozoites. 
It has also been suggested that the large forms of the gurnard 
haemogregarine show sexual differentiation, the long thin forms with a 
small nucleus being of male character, and the broad bean-shaped forms 
with a large nucleus being of female sex. Also, the large forms are 
taken to represent an old infection, while the small oval forms are 
taken to represent a new or recent infection. Such an interpretation 
is merely a matter of conjecture, for we have no knowledge of the time 
necessary for the full development of a piscine haemogregarine either 
in the tissues or in the red corpuscles. 
If the large forms do show sexual differentiation, then one must 
assume the existence of a cycle such as occurs in the Haemosporidia, in 
which sexual features appear only in the last generation of a schizogony 
where normally no sexual dimorphism occurs ; or, one must assume that 
there occurs a cycle such as has been found in some of the coccidia, a 
cycle in which micro- and macroschizonts give rise to a crop of micro- 
and macromerozoites. Nor is it possible to pronounce definitely in 
favour of either of these assumptions—although the first is probably 
the correct one—till the opportunity presents itself not only of examining 
the tissues of the vertebrate host but also of tracing the phases 
of development in an invertebrate carrier. 
On the gills of all the catfish examined there occurred a leech which 
was sometimes present in enormous numbers. This leech has not been 
definitely identified, but from a superficial examination of several 
specimens Miss Muriel Robertson was kind enough to suggest that it is 
probably Trachelohdella lubrica. Several examples of this leech have 
been examined in carefully prepared serial sections, but no develop¬ 
mental phases have been found, though it is likely that it is the actual 
carrier of the infection, for a leech, Ozobranchus Shipleyi, has been 
proved to be the carrier of a haemogregarine infection in the case 
of the common lake tortoise of Ceylon, Nicoria trijuga (Robertson, 1910). 
One must not, however, overlook the possibility of a haemogregarine 
infection in fish occurring through the alimentary tract from ingestion 
of an intermediate host, as is described by Miller (1909) for Hepatozoon 
perniciosum. 
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