98 W. G. RIDEWOOD AXD H. B. FAMTHAil. 



sporulea (pansporoblasts giving rise to a number of spores) 

 and the Oligosporulea (pansporoblasts giving rise to a few 

 spores or to a single spore eacb) . 



The systematic position of Neurosporidium is as follows: 

 Phylum. — Protozoa . 

 Class. — Sporozoa. 



Sub-class. — Neosporidia. 

 Order. — Haplosporidia. 



Section. — Polysporulea (nov. sec). 



Genus. — Neurosporidium (nov. gen.). 

 Species. — cephalodisci (nov. sp.). 



EXPLANATION OF PLATES 6 AND 1, 



Illustrating Dr. Ridewood and Mr. Fantham's paper on 

 Neurosporidium cephalodisci, n.g., n. sp., a Sporo- 

 zoon from the Nervous System of Cephalodiscus 

 nigrescens." 



PLA.TE G. 



Por the two photomicrographs from which figs. 1 and 2 were drawn we are 

 indebted to Dr. N. H. Alcock, Lecturer on Pli^siology in St. Mary's Hospital 

 Medical School, and to him we hereby tender our best thanks. The pholo- 

 graphs were taken by monochromatic liglit obtained by a Thorpe's grating, 

 and Zeiss's apochromatic objectives were used. 



Tig. 1. — Section of a polypide of Cephalodiscus nigrescens taken 

 transversely to the length of the body, and passing behind tlie pedicle of tlie 

 buccal shield and behind the mouth, x 120. Nsp. Neurosporidium in 

 the tliick ventral wall of the buccal shield, ph. Wall of pharynx, t.c. Trunk 

 coelom. m. Muscles of the ventral body-wall. 



Fig. 2. — Section of a polypide of Cephalodiscus nigrescens taken 

 transversely to the length of the body, and passing through the central nerve 

 mass and the notochord. X 100. Nsp. Neurosporidium in the central 

 nerve mass. s. Septum between the right and left collar cavities, no. Noto- 

 chord, p.c. Proboscis cavity, or cavity of the buccal shield, b.s. Thick 

 ventral wall of the buccal shield. Iph. Base of the lophophore, cut obliquely. 

 a. Ectoderm around the anus, cut tangentially. 



