28 MARINE AND FISHERIES 



5 GEORGE V„ A. 1915 



ation of freed individuals showed the attachment to be brought about by short 

 pseudopodia at the anterior end. In the parasite of Zoarces angularis the 

 attachment is probably to the epithelium of the gall bladdeer, since the fine 

 pseudopodia are found and the myxosporidium found in U. chuss seems to be 

 absent. In the parasite of Pseudopleuronectes americanus no attachment has 

 been seen. The dimensions of a typical myxosporidium are: — 



Length, excluding tail 12-25 fj, 



Width 10-20 ;x 



Tail up to 60 ;i 



In studying the structure of the spores of the Myxosporidia it is convenient 

 to use the method of orientation employed by Thelohan ('95, p. 250-251) and 

 generally adopted by subsequent writers. Where there is a single polar capsule 

 or two (cps. pol. Fig, 1) or more close together the part of the spore in which the 

 capsules lie is called anterior (a Fig. 1). The plane (pa Fig. 1) passing through 

 the suture separating the two valves is called the sutural plane. The spore is 



. ,cps.pol- 



/ 

 / 

 / 



a' 



a 



P 



I r 



Fig.l 



Fig. 1. Spore of Ceratomyxa acadiensis n. sp. drawn to show method of orien- 

 tation and nomenclature. Explanation in text. X 2000. 



orientated by placing it with the polar capsules in front and the sutural plane 

 vertical (Fig. 1). Then the front is anterior and the part behind is posterior 

 (p Fig. 1), the upper surface dorsal and the lower surface ventral, the right 

 side the right and the left side the left. The sutural diameter (Thelohan '95, p. 

 251) is the greatest diameter in the sutural plane. The bivalve axis (1 r. Fig. 1) 

 is the line which measures the greatest distance between the two valves perpen- 

 dicular to the sutural plane. 



The general shape of the spore of Ceratomyxa acadiensis n. sp. (Fig. 1) may 

 be described as that of a spindle, of which the longitudinal axis has been bent into 

 an arc of a circle. The chord of this arc is the bivalve axis, and may be called the 

 width of the spore. The convex side of the arc is anterior, the concave side poster- 

 ior and the opposite ends right and left. The sutural axis extends in the antero- 

 posterior direction and is equivalent to the length of the spore. The two valves 

 are cone-shaped, the pointed ends being directed one to the right and the other 

 to the left and the bases meeting in the plane of suture. The spore is slightly 

 compressed dorso-ventrally. A slight variation in the form and dimensions of 

 opposite valves of the same spore was often noticed. The lateral filaments, ex- 

 tending outward from the tips of the valves on either side, are very long and thin. 



