497 



ON TWO REMARKABLE SPOROCYSTS OCCURRINU 



IN MYTILUS LATUS, ON THE COAST OF 



NEW ZEALAND. 



By Professor W. A. Haswell, M.A., D.Sc, F.R.S. 



(Plates xix.-xx.) 



The parasites which form the subject of the present communica- 

 tion were found by me last summer in specimens of a species of 

 Mytilus (M. latus) living on the coast of New Zealand. I am 

 greatly indebted to Dr. Chas. Chilton, Acting Professor of Biology 

 at Canterbury College, Christchurch, for subsequently procuring 

 and sending me a large consignment of live specimens of the 

 mussel. 



The Spokocysts of an Echisostomum. 



The Sporocysts, in which the Cercarise are developed, were 

 found in a fairly large proportion (about 10 per cent.) of the 

 mussels examined, and always in large numbers. They infest the 

 mantle-folds and the region immediately in front of the posterior 

 adductor muscle, and are most abundant in the gonads and 

 nephridia. In infected mussels this region of the body is coloured 

 bright red owing to the presence of hundreds of the Sporocysts, 

 which contain a conspicuous red substance to be referred to 

 below. 



From the fact that such large numbers of the Sporocysts occur 

 together, it is to be inferred that they multiply actively in the 

 tissues of the mussel. This multiplication of Sporocysts takes 

 place not only by budding, or rather binary fission, but also, 

 though comparatively rarely, by a process corresponding to that 

 by which in many, if not most, Sporocysts Redia^ are developed. 



