THE MYXOSPORIDIA OF THE BEAUFORT REGION. 209 



In the case of species inhabiting the gall or urinary bladders it is, of course, a simple 

 matter for the spores to reach the exterior. I have many times observed the spores of 

 gall parasites in the intestine and rectum, whence they doubtless pass out with the feces. 

 That the spores formed in the gall and urinary bladders pass out quickly after being set 

 free is indicated by the fact that free spores are always comparatively rare in such cases, 

 although there may be an abundance of sporulating trophozoites present. 



It is interesting to note in this connection that, in many species at least, adverse 

 conditions tend to hasten the process of sporulation. It has often been observed that 

 after the death of the host or after being removed to the slide those trophozoites in which 

 sporulation is well advanced mature their spores in a very short time. Such spores are 

 often smaller than those formed under normal conditions. 



It is obvious that in the tissue parasites the spores in many cases will not be able to 

 reach the exterior until after the death and disintegration of the host. In other cases, 

 however, the cysts may break open either on the outer surface or into some cavity of the 

 body, whence they may easily make their escape. In a number of instances spores of 

 Myxobolus in the gall bladder and intestine have been noted. 



After reaching the exterior the spores are apparently dependent on chance in enter- 

 ing a new host. There is no evidence of secondary or intermediate hosts, although such 

 a possibility is by no means excluded. On the theory of purely accidental infection it is 

 somewhat difficult to account for the high percentage of infection met with in many 

 instances. For example, although a large number of individuals of the squeteague, 

 Cynoscion regalis, were examined, not one was found infected with Sinuolinea dimorpha. 

 The gall bladder of the pipefish, Siphostonia floridce, is always infected with Sphmrovtyxa 

 balbianii, although in this case an infection of 100 per cent is not so difficult to explain on 

 account of the feeding habits of the host. Similarly, the gall bladders of sharks and rays 

 are, except in the case of very young individuals, practically always infested with one or 

 more species of Myxosporidia. It has been suggested that the processes of various kinds 

 with which so many of the spores are provided enable them to float for a much longer 

 time and thus increase the chances of their being taken into the proper host. 



So far as known the spores do not germinate until after reaching the stomach or 

 intestine of the host. This would seem to decrease the chances of infection to a consider- 

 able extent, since most of the spores carried into the mouth in breathing would in all 

 probability be swept out again through the gill openings. It would be interesting to 

 follow the fate of the spores in case the host is devoured by another fish. 



On reaching the intestine the valves of the spore separate under the influence of the 

 digestive fluids, allowing the sporoplasm to creep out as a minute amocbula, which by 

 actively crawling along the ducts or by entering the blood vessels finally gains access to 

 the organ in which it is destined to undergo further development. The action of the 

 digestive fluids has been shown by Auerbach, Thelohan, and others to cause the extru- 

 sion of the filaments from the capsules. It has been supposed that the function of these 

 organs is to attach the spore to the wall of the gut, but it would seem much more prob- 

 able that the filaments would simply become entangled in the partly digested food and 

 swept along toward the rectum. Since in the few cases in which the germination of the 

 spore has been investigated the sporoplasm emerged in a very short time after the spore 



