DISEASE OF THE HERRING 83 



SESSIONAL PAPER No. 38a 



in with food particles, or parasitic on the bodies of animalculae on which the herring 

 feeds. The life-history is very complicated, and the cycle of changes and apparent 

 metamorphoses it undergoes surprising, as a glance at the figures appended to this 

 paper will show. For the unravelling of these processes and determining the species,- 

 living material is essential, and even then it is one of the most difficult studies a 

 micro-biologist can undertake. 



It seems to be a Neosporidium, a member of a group of Myxosporidia which are 

 propagated by means of spores. The spores are provided with a dense ectosarc which 

 rierves as a protective cell-wall, and are technically known as "sporon's" The 

 envelope is digested in the stomach or enteric canal and the parasite liberated in the 

 form of an amoebula, which, partly owing to its minuteness and partly to the power 

 of altering its shape to suit conditions, penetrates the epithelial lining, enters the 

 blood-currents, and is carried to the special tissues to be infected. This amoebuloid 

 form has been designated by Stempell a " planont," from the wandering habit ; and 

 the one under discussion seems to be intercellular, that is, occurs very generally 

 lodged among the fibres of tissues, especially of the muscular and vascular tissues, 

 which may become wholly disintegrated or destroyed by enormous swarms of the 

 parasite. Constantly bathed in lymph, the Neosporidium ingests its food by absorp- 

 tion alone, so that the pseudopods seem to aid the parasite in insinuating itself among 

 the fibres and increasing the extent of absorbing surface. Under these favourable 

 conditions it multiplies in a surprising manner. 



Though the life-history of the parasite could not be satisfactorily made out, the 

 absolute character of some phases could; and reading in between them the scanty 

 knowledge of the group available, certain relations of these phases were rendered 

 probable. For instance figs. 11, 12, 13, and 14 plainly suggest a succession, eleven 

 , being theoretically the initial stage of the series. It is clearly a Plasmodium or multi- 

 nucleate cell, to be presently resolved into a large number of uninucleate cells, known 

 as " meronts " and represented by fig. 13, rounded off in fig. 14. The multi-nucleate 

 cell is generally believed to arise from the sporont, and some evidence to that effect 

 was obtained during the study of the material, but the structure of the sporont made 

 the initial steps of the development hard to follow. For instance: instead of the 

 chromatin being more or less aggregated into a nucleus and a near nuclear investment, 

 it was largely distributed through the whole cytoplasm in the form of granular 

 chromatids and obscured more or less with melanin, so that the nucleus, even when 

 stained, could be seldom seen, and hence the first stages of nuclear division were not 

 clearly made out. Indeed some authors doubt that the sporont possesses a nucleus at 

 all. It was only when the division of the nucleus, if it has one, had advanced some- 

 what, or the wandering chromatids had been attracted to certain points (multi- 

 nuclear centres) that the phase became evident. Again, it could not be determined 

 whether the multi-nucleate cell arose asexually or was the result of a previous conju- 

 gation of gamete sporonts. It undoubtedly represents one method of rapid multipli- 

 cation. 



Few instances of binary fission were met with, one of which is represented in fig. 

 19, but many of the protean forms suggest budding, a condition rendered quite prob- 

 able on account of the nuclear elements being scattered throughout the whole cyto- 

 plasm. Indeed many of the pseudopodial enlargements were seen to be rounded 

 distally and the chromatids more or less aggregated after the manner of an ill-defined 

 nucleus, the whole suggesting new cell-formation by gemmation. 



While all stages were to be found in any affected tissue, the meronts were most 

 abundant in that least affected ; the sporonts or resistant spores, where disintegra- 

 tion was most advanced; and the planont stage largely characterized the blood, liver, 

 intestines and kidneys, though in the latter confined to the blood vessels. 



Contamination is effected by the sporont, or at least such is the general belief, 

 but the precise manner of transmission is in doiibt. Granted some means of con- 

 s'-; a— 6^ 



