THE PARASITE MINCHINIA. 447 



advanced cases were found to have lost their reserve food and to 

 be much reduced in size. In spite of the necrotic condition of 

 this organ, however, the life of the Chiton appeared to be little 

 affected — at any rate, in captivity infected specimens sometimes 

 lived longer than non-infected. No observations appear to have 

 been made on the normal length of life of a Chiton, possibly it 

 may be great. Quite small specimens are often sexually mature; 

 on the other hand, strongly infected specimens are nearly always 

 very large — some of them the largest specimens ever seen at 

 Plymouth. Could it possibly be that development of Minchinia 

 in a Chiton causes the whole animal to hypertrophy ! On the 

 whole, adult forms were better infected than young ones, as would 

 be expected. I have not seen the earliest stages of infection, but 

 presumably the Chiton become infected when feeding : the}' are' 

 said to be entirely vegetarian. Labbe has figured three (10, text- 

 fig. 107) so-called sporozoites in the liver-cells; possibly one of 

 them is something of the kind, the other two appear to be the 

 normal contents of the liver-cells. Many experiments by which 

 I have tried to infect Chiton artificially have given negative 

 results. Ripe spores have not been induced to open when intio- 

 duced into the oesophagus or placed in fluid from different regions 

 of the alimentary canal. Therefore ^VQ seem forced to the 

 conclusion that there is another host ; this, at the beginning, 

 seemed unlikely : first, because the , spores as developed in 

 Chiton are so admirably adapted for an external free existence, 

 and secondly, it is not easy to see how such an animal as Chiton, 

 which feeds on plants, could easily become infected from other 

 animals. Certain other facts in this connection are given below 

 after the description of the spores. 



Methods. 



Bouin's picro-formol-acetic mixture was found to be the best 

 fixative for infected tissue, since this penetrates to a certain 

 extent even into ripe spores. The special methods applied to these 

 spores will, however, be described later when considering their 

 structure. For general purposes picro-nitric and corrosive 

 sublimate mixtures were also satisfactory. Owing to the small 

 size of gametes, sporoblasts, and young spores, it was necessary to 

 have thin sections (3-4 jx), and when there were many chitinous 

 spores this was not easy. Breaking of sections was sometimes 

 prevented by painting with collodion. For following the 

 development of the spores it is essential to have living material, 

 and methyl-green and acetic acid mixture was used for temporaiy 

 preparations. Numerous coverslip films and smears stained 

 with Giemsa were also used for studying the development. For 

 staining films and sections iron hfematoxylin or haematein methods 

 are of course most useful ; water solutions certainly seem to give 

 better results than the alcoholic ones recommended by Lee (12, 

 p. 156) and others, though by the latter staining is more speedily 

 effected. The chitinous sul)>tance forming the spoi'e coat stains 



