632 TRANSACTIONS OF SECTION D. 



Abstract of Freezing-point Determinations. 



°C, 



A of sea water —1-91 



A of egg-contents of Plewonectes platesm .... — - 70 



A of blood of P. platessa — 0"75 



A of egg-contents of dog-fish eggs — 1-80 



A of blood of adult fish. -1-90 



2. Coccidia and Coccidiosis in Birds. 

 By H. B. Fantham, D.Sc, B.A.. A.R.C.S. 



One of the great causes uf death in young birds, such as grouse and pheasants, 

 is popularly known as 'enteritis,' one of the symptoms being diarrhoea. The 

 term enteritis has been used to cover many intestinal derangements, but one of 

 the chief forms of it is now known definitely, and has also been proved 

 experimentally to be due to Coccidia, microscopic, parasitic Protozoa belonging 

 to the class Sporozoa. The pathogenic agent in grouse, fowls, and pheasants is 

 known as Eimeria (Coccidium) avium. 



Coccidia are responsible for fatal epizootics among grouse chicks, pheasants, 

 fowls, turkeys, geese, ducks, and other birds, and hence the study of the 

 pathogenic organisms is of great economic importance. Resistant oocysts of the 

 parasite are voided in the fa?ces of the infected birds, and are acquired by other 

 birds in their food or drink. A mature oocyst contains four sporocysts, in each 

 nt which two active, motile germs or sporozoites are developed. The oocysts arc 

 swallowed by the birds, and under the influence of the pancreatic juice the cyst 

 walls are softened, the sporozoites creep out and penetrate the epithelial cells 

 of the duodenum of the host. There they become rounded and grow, passively 

 feeding on the host cell. 



After attaining a certain size, the parasites — now schizonts — proceed to 

 multiply. Nuclear division occurs, the nuclei migrate to the periphery of the 

 cell, cytoplasm segregates round each nucleus, and a cluster of daughter germs 

 or merozites arranged "en bardlet," i.e., like the segments of an orange, is 

 produced. Very little residual protoplasm remains after the formation of 

 merozoites. The groups of merozoites break up and the small, vermicular 

 parasites glide away and invade other cells, there to grow and multiply in 

 exactly the same way as did their parent cell. A number of generations of 

 merozoites is produced, and the destruction of the epithelium, due to their action 

 and the digestive derangements resulting therefrom, are sufficient to cause the 

 death of the host in some cases. But in most instances some merozoites pass clown 

 into the caeca, where they grow and multiply, producing intense inflammation. 



Sooner or later a limit is reached both to the power of the bird to provide 

 nourishment for the parasite and to the multiplicative capacity of the parasite 

 itself, and then sexual forms are produced. Some Coccidia become large and 

 massive and contain much reserve food-material. These are the macrogametocytes 

 or female mother cells, each of which gives rise to a single macrogamete (? ). 

 Slightly smaller parasites (microgametocytes) undergo nuclear multiplication and 

 give rise to many minute, biflagellate microgametes {$). The groups of microga- 

 metes disperse and each microgamete swims away in search of the macrogamete. 

 The latter invests itself precociously with a cyst wall, in which a inicropyle is 

 left for the entry of the microgamete. One microgamete only fuses with the 

 macrogamete — the process has been watched in life — and the oocyst wall is then 

 completed by the closure of the micropyle. The oocysts may vary somewhat in 

 size and shape. 



At first the oocysts are uninucleate and their contents completely fill them. 

 The contents then concentrate into a spherical mass, either at the centre or 

 nearer to one end. The nucleus divides into four, and around each nucleus 

 protoplasm aggregates, forming four round sporoblasts. Each sporoblast develops 

 into an oval sporocyst, inside which two sporozoites are formed. 



Coccidiosis is accompanied by an increase in the number of polymorpho- 

 nuclear leucocytes in the blood, together with a decrease in the number of the 

 erythrocytes. 



