GILLS OF LAMELLIBRANCH MOLLUSCA. 43 



The Minute Structure of the Gills of Lamellibranch 

 MoLLUSCA. By E.. Holman Peck, F.L.S., Scholar of 

 Exeter College, Oxfoid. (With Plates, IV, V, VI, VII.) 



The investigations of which the result is here given were 

 undertaken at the suggestion and under the guidance of Mr. 

 Ray Lankester, and Avere carried on during the past year in 

 the Histological Laboratory of Exeter College, Oxford. 

 Specimens of Mytilus and of Cardium were kindly procured 

 for Mr. Lankester by Mr. Charles Stewart, the talented 

 curator of the museum of St. Thomas' Hospital, and their 

 investigation was commenced prior to Christmas, 1875; 

 Anodon and Dreissena are abundant in the neighbourhood of 

 Oxford ; Area, Pectunculus, Spondylus, Solen, Mactra, and 

 other genera were obtained by me through the good offices of 

 the staff of Dr. Dohrn's zoological station at Naples, when I 

 visited that establishment in the winter of 1875 — 76. My 

 observations and notes have continually been controlled by 

 Mr. Lankester, a few of the drawings in the plates were made 

 by him, and the nomenclature, wherever it is new, is sug- 

 gested by him. 



Since the introduction into comparative anatomy of the 

 searching methods of histological inquiry, there has been but 

 one memoir published devoted to the consideration of the 

 Lamellibranch''s gill, viz., that of Dr. Carl Posner, which 

 appeared in the ' Archiv fur Mikr. Anat.,' vol. xi, p. 517 

 (towards the end of the year 1875). My observations were 

 commenced independently of that writer's results, and have 

 led me to conclusions at variance with his on many points, 

 as will appear in the sequel, Posner has given histological 

 details with regard to the gill of Anodon only, and has con- 

 fined his statements relative to the other Lamellibranchs to a 

 series of highly instructive and^ in the main, accurate dia- 

 grams of the types Mytilus, Ostraea, Pinna, Venus, Pholas, 

 Scrobicularia, Mya, Solen, and Pecten. 



The present communication will deal with the structure of 

 the gill in the genera Area, Mytilus, Dreissena, and Anodon. 

 In a subsequent memoir it is my intention to deal with other 

 types. — ^ 



Without going into a full history of our knoAvledge of the 

 structure of the gill-plates of Lamellibranchia, it is yet 

 desirable to cite some of the writers whom we have to thank 

 for the knowledge at present embodied in text-books of com- 

 parative anatomy. Cuvier and the zoologists of his genera- 



