450 Benjamin Sharp 



W. Keferstein 1 investigateci the eye of Pecten maximus and en- 

 tered into a detailed account of tbe minute structure and supposes , as 

 does Leydig^. that it closely resembles a compound arthropod eye. 



V. Hensen^ in 1862 gave by far tbe most complete account tbat 

 we bave of tbe eye of Pecten. He investigated tbe eyes of Pecten jaco- 

 haeus and Area sp. (?) He entered into a minute account of tbe anatomy 

 and bistology of tbe eye a summary of wbicb will be given later in its 

 proper place (p. 456) . He also investigated tbe forms described as 

 possessing eyes by Will , but was in tbe majority of cases utterly un- 

 able to find any trace of visual organs ^. 



In tbe last edition of C. Gegenbaue's Comparative Anatomy ^ be 

 says, after considering tbe embryonic eyes of tbose mollusca wbicb 

 are blind in tbe adult state, tbat Ai-ca^ Pectunculus, Teilina^ Pinna etc. 

 bave tbe organs (eyes) on special optic stalks : tben after referring to 

 Pecten anà Sponclt/Ius, be says: »Altbougb tbese organs bave many 

 peculiarities of structure , tbey agree in all essential points witb tbe 

 optic organs of the rest of tbe Mollusca<i . 



S. J. HiCKSON^ in ISSO takes up tbe eye oi Pecten j'acohaeus^ 

 P. opercularis and P. inaximus considering carefully tbe minute ana- 

 tomy. He differs from Hensen in some points regarding tbe lens. 



E. 0. Schmidt" in 1SS2 gives a short general account of tbe eye 

 oi Pecten sp. ('?) and rather doubts tbe fact of its being purely an 

 organ of vision , obser\iug that it is quite possible tbat it bas anotber 

 signification. 



Tbe last paper hearing upou tbis subject is a short note on the 

 eye of a species of Spomhjlus by S. J. Hickson (1SS2) s. He fìuds tbat 



1 W. Keferstein , Untersuchungen über niedere Seethiere. § IX. Über den 

 Bau der Augen von Pecten. Zeitschr. f. wiss. Zool. Bd. XII. Leipzig 1862. p. 133 ff. 



2 Fr. Leydig, Lehrbuch der Histologie der Menschen und der Thiere. 

 Frankfurt a. M. 1S5T. 



3 V. Hexsex , Über das Auge einiger Cephalopoden. Zeitschr. f. wiss. Zool. 

 Bd. XV. Leipzig 1865. p. 220 ff. 



* p. 221 Anm. : »Es wäre mir sehr lieb gewesen, wenn ich noch einmal frische 

 Augen hätte prüfen können, aber bei erneuter und, wie ich meine, sorgsamer Prü- 

 fung der Auster und bei früherer Prüfung von Mya und Cardium habe ich trotz 

 Will's Angaben keine Augen finden können.« 



5 C. Gegenbaur , Elements of Comparative Anatomy. Engl, edition by 

 F. Jeffrey Bell. London 1878. § 272. p. 353. 



6 S. J. HiCKSox, The eye oi Pecten. Quart. Journ. ofMicr. Sc. N.S. Vol. XX. 

 London 1880. 



■^ E. 0. Schmidt, Handbuch der vergleichendeuAnatomie. 8. Aufl. Jena 1882. 

 s S. J. Hickson, The eye oi Spondylus. Quart. Journ. of Micr. Sc. N. S. 

 Vol. XXII. London 1882. 



