antenai, and longitudinal spiral rows of short, stout cilia. They 

 did not appear to damage the diverticula. 



Sporozoa were present in the diverticular epithelium of 16 (12.4%) 

 of the specimens examined. All but two of the cases were from Aber 

 Benoit or Rade de Brest and lie Tudy (Table 3). Sporozoans were spher- 

 ical and stained very intensely. They were often surrounded by a clear 

 (lysed ?) zone. 



The digestive gland of one specimen bore a nematode which elicited 

 an inflammatory response, an aggregation of eosinophilic leucocytes. 



Remains of copepods were noted in the diverticula of 3 C. gigas 

 from Aber Benoit. They were accompanied by heavy leucocytic inflammation 

 and were being phagocytized as evidenced by the presence of leucocytes in 

 the copepods. 



3. Gut . - Samples consisting of stomach, intestine and often esoph- 

 ageal and rectal tissues were examined from 127 C. gigas. Generally, 

 two tissue samples were taken from each specimen (anterior and posterior 

 portions of the visceral mass). 



Histopathologies were noted in 32.2% (41 of 127) of the gut samples 

 examined. There were 62 cases of the 6 pathology types discussed below. 

 Thirty-five percent (22) involved a symbiont while 40 cases (65%) 

 apparently were not symbiotic in nature, although there may be some 

 question about this. Specimens from the combined reference stations bore 

 more than two and a half times the pathologies as Aber Wrac'h specimens. 

 Oysters from Aber Benoit contained slightly fewer pathologies than those 

 from the reference stations and twice the number of pathologies as speci- 

 mens from Aber Wrac'h. 



Abnormally high numbers of eosinophilic leucocytes (general leuco- 

 cytosis) were noted in the intestinal epithelium, and sometimes surround- 

 ing leydig tissue, of 15% (19 of 127) of the C. gigas examined. Almost 

 all cases were in oysters from Rade de Brest. This condition was diffi- 

 cult to judge. Oyster intestinal epithelium normally has some leucocytes 

 between columnar cells. However, the large number of leucocytes in the 

 intestinal epithelium of these 14 specimens appeared abnormally high, 

 the number was considered abnormally high if the basal portion of columnar 

 cells was completely, or almost completely, obscured by leucocytes. 

 However, there still is some doubt about whether- this is a "pathology" 

 or a normal condition. Except for the large number of leucocytes, the 

 intestinal tissues appeared very healthy. 



279 



