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POST-LARVAL, FIXED OR SPAT STAGES 



Difficulty of Discovery when Very Young. — The pre-larval or embryonic 

 stages are free but incapable of locomotion, the larval stages free and loco- 

 motory, while the post-larval or spat stages are offset from any of the pre- 

 ceding by being normally attached or fixed to shells, rocks or other solid 

 submarine objects. From this time onwards there is no further change in 

 the method of living, the spats growing up regularly into adult oysters 

 (Plates II and III). 



Oyster consumers, merchants, fishermen, culturists, are all aware 

 that it is possible to begin with the largest oyster and pick out a series 

 descending in size to those of very small dimensions. Such terms as 

 "large," "medium," "small," may have very different meanings, accord- 

 ing to the judgments of the people using them; but sooner or later the 

 youngest oysters of the series become so small, irregular and variable, as 

 to be with difficulty distinguished from several other species with which 

 they occur. We may, I suppose, regard this size as approximately that 

 of a man's thumb-nail. Oysters smaller than this require greater care, 

 more knowledge of other animals, and more special technical application 

 than most people possess. I have known men who were brought up 

 in oyster districts and used to fishing or handling oysters all their lives 

 who had never sought out young stages; men interested in oyster 

 questions have shown me objects (stones, shells, bark, &c.) with 

 supposed oyster spat attached that were not oyster-spat at all; a 

 culturist, who had been very successful for upwards of twenty years 

 in the management of large spat, had never learned to recognize 

 the minute young spat; a professed zoologist, working on the subject, 

 and presumably acquainted with many types of animals and the 

 methods of studying them, mistook for spat scale-insects on brush 

 that had been put out for their capture. There are statements of 

 observations that may have been made in good faith that, because of 

 too narrow an acquaintance with the subject, refer to wrong animals. The 

 careful investigator cannot trust anything but what is accompanied with 

 sufficient detail to prove that the observer had a first-hand knowledge 

 of his subject and that he had the proper objects before him. The greatest 

 lack in the literature is detail. Off-hand, empirical statements are mis- 

 leading, since they do not bear the evidence of being either theoretical or 

 practical. It would have sometimes saved succeeding investigators end- 



