>rotes on a New Boveria, species. 2^1- 



In passing the bacterial infection of the Boveria, which is 

 occasionally observed, may be mentioned. We have here to do 

 with a Bacillus form, of which large numbers generally accumulate 

 in the neighbourhood of the meganucleus. The parasites are 

 strongly stained by Delafield's hœmatoxylin and by iron-alum 

 haëmatoxylin, and are easily liable to be mistaken for chromidial 

 bodies. They do not seem to cause any serious harm to the host. 



V. Encystment. 



Boveria labialis was observed by us to encyst in the sub- 

 epithelial connective tissue of the respiratory tree of the host. 

 The encystment seems to occur when the parasites have had to 

 live under certain unfavourable conditions, for instance, when the 

 water in the respiratory organ has become poor of oxygen. This 

 may be occasioned by the host long remaining in a forcibly con- 

 tracted state or in the air during low tide, or when a shortage of 

 food has set in, probably owing to excessive multiplication of the 

 parasites. 



Ordinarily the encystment proceeds in the w^ay to be describ- 

 ed below and illustrated semidiagrammatically in fig. 20. Any' 

 individual about to encyst first attaches itself always with its 

 aboral end to the inner epithelium of the respiratory tree. Then- 

 it penetrates the epithelium and begins to sink gradually deeper- 

 in the subepithelial connective tissue (see the individual A). After 

 having completely burrowed into the connective tissue, the organ- 

 isin gradually and strongly contracts its own body (the individual 

 jB.) During this contraction period the organism loses the peri-- 

 stomal disc, the contractile vacuole, the meganucleus, and food 

 vacuoles," consequently the micron'ucleus aiid the cilia on the 

 general body -surface "represent the only visible ' organs. The ciliaj 

 not only persist but become gradually longer and later even thicker,- 



