LARVAL OR SWIMMING STAGES 41 



bivalve larvae had not been distinguished, and it was only possible to guess at which 

 was which." 



Nelson (1903, p. 435) "discovered many swimming, shelled embryos in the high- 

 tide water. These were secured by filtration through Schleicher and Schiill filter 

 paper." 



Nelson (1906, p. 316) : "In order to ascertain whether or not oyster fry are present 

 in the water it is necessary to filter it through a fine filter, which is a slow process." 



McBride (1904, p. 151, 153): "But judging from the size of the free-swimming 



larvae caught by the tow-net During the latter part of the month 



(August) the waters were swarming with larvse, which from their exact agreement in 

 shape and appearance with the larvae of the European oyster, were doubtless the later 



stages of the free-swimming young of the Malpeque oyster The later 



larvae which were captured by the tow-net are characterized by possessing a straight- 

 hinge to the shell totally unlike the hinge of the adult Fig. 4. 'Late larva 



of the oyster captured by the surface-net.' " 



These statements might have passed if the author had not inserted a figure. This 

 shows at once that the larva was not a late larva, at least in the sense of being old, 

 which, when taken in connection with the words "later stages", must have been the 

 one intended. In the sense of being late in the season the statement does not corres- 

 pond with what I found at the same place in the succeeding year. Upon examining 

 "Fig. 4" closely I found that it was not an oyster larva at all. The measurements are 

 83, 70, 51 mm., which, if divided through by a common divisor such as will reduce the 

 length to that size of my series corresponding in shape and structure, will give 15, 12-6, 

 9-2 as the length, height and hinge-line. Referring this to the table of comparison of 

 a mussel, a clam and an oyster at this period (p. 36), it becomes evident that it could 

 have been no other than the larva of the common clam. This conclusion is also borne 

 out by its small size so late in the season (clams continuing to breed late), its shape, the 

 one end being larger than the other, the relatively long hinge-line, and the chances that 

 it would be one of the commonest of larvae in the water about the station. Clams live 

 in the mud along the beach below where the station stood. 



Neither can " Fig. 3" be the larva of an oyster, because of the single otolith figured 

 in each otocyst, which is true for the clam but not for the oyster. Single otoliths are 

 present in clams, quohaugs and scallops; numerous otoconia in mussels, silver-shells and 

 oysters; which of course could not be known without an extensive study of these bi- 

 valve larvae. The expression " Otocysts here recorded so far as I am aware 



for the first time" is very similar to the statement of Lacaze-Duthiers (1854, p. 1200). 



"Enfin j'ai vu apparaitre les otolithes quelques globules agites de mouve- 



ments dont personne n'avait meme constate l'existence." The words "quel- 

 ques globules" show that Lacaze-Duthiers had observed the character of the otoconia. 



Notwithstanding the mistaken identity of species the author thought he saw an 

 "exact agreement in shape and appearance with the larvae of the European oyster." 



It is announced that, "It was my special object at Malpeque to determine the time 

 at which the oyster became sexually mature, as it is the object of the Government so 



to frame its regulations as to protect the oyster during this period of its existence 



When I commenced to take observations at the end of July, etc." The author made 

 the mistake of commencing a month to six weeks too late to accomplish the proposed 

 •object, which occasioned still other mistakes besides those referred to. 



