80 RICE. 



disposal. Only in the figures is a possible hint of its observation. 

 Thus in the exquisite work by Deshayes 1 on the Mollusca of 

 Algiers there is a small figure of the gill of Pholas, in which two 

 incomplete filaments are interpolated among those which extend 

 through the whole height of the gill. In the one the free end 

 is turned upward ; in the other, downward. Do these represent 

 two filaments fusing with their neighbors ? If so, the difference 

 in direction in the two cases clearly distinguishes the phe- 

 nomenon from that described above. Moreover, the author's 

 description of the gill as entirely smooth makes a fusion 

 a priori improbable. An inaccuracy in the drawing, which is 

 very small, is the simpler explanation. 



In a considerable number of more recent figures a single fold 

 of the gill is represented in section as containing an unequal 

 number of filaments in the two lamellae, thus in Cardium 

 (van Haren), 2 Lima (Pelseneer), 3 Dona.v trnncnhis (Sluiter), 4 and 

 Ostrea (Kellogg). 5 It will be noted that in the last two cases 

 the figures cited do not accord with my own observations. But 

 my purely negative verdict of " not observed " contains no direct 

 contradiction of the affirmative statements of these authors. 

 While I am convinced that my own preparations show no evi- 

 dence of a fusion of filaments in Ostrea and Donax trunculus, I 

 consider it probable that the figures of Kellogg and Sluiter, as 

 well as those of van Haren and Pelseneer, point to a greater or 

 less development of the phenomenon described. Unfortunately 

 no certain conclusions can be reached in the absence of corrob- 

 oration in the accompanying text. 



1 Deshayes, G. P., " Exploration scientifique cle 1'Algerie," Zoohgie. Tome i, 

 No. 4. Paris, 1849. 



- Haren-Noman, D. van, "Die Lamellibranchiaten, gesammelt wahrend der 

 Fahrten des Willem Barents, 1878 and 1879," A T iederlandisches Archiv fur Zoologie. 

 Supplementband I, 1881-82. 



3 Pelseneer, P., "Contribution a 1' etude des Lamellibranches," Archives de 

 Biologic. Tome xi. 1891. 



4 Sluiter, C. P., " Beitrage zur Kenntniss des Baues der Keimen bei den Lamelli- 

 branchiaten," Niederlandisches Archiv filr Zoologie. Bd. iv. 1878. 



5 Kellogg, J. L., " A Contribution to our Knowledge of the Morphology of the 

 Lamellibranchiate Mollusks," Bulletin of the U. S. Fish Commission. Vol. x. 1890. 



OHIO WF.SLEYAN UNIVERSITY, DELAWARE, OHIO. 



