New Series, No. 218 (Vol. 55, Part 2). Price lOs. net. 



Subscription per volume (of 4 parts) 40s. net. 



JUNE, 1910. 



THE 



I 



qUarterlv journal 



OF 



MICROSCOPICAL SCIENCE. 



KOITKI) KY 



Sir ray LANKESTER, K.C.B., M.A., D.Sc, LL.U., F.R.S., 



HUNUHAKY KKI.LOW OP KXETEK C O M-K G H , O X t O K U ; C OK U K8 P (»N D B N T OF TUB 1N8TITUTK OF FKANCK, 



AND (IF THK IMFICRIAI. ACADEMY o" SCIK^CES OP ST. PETEK8BUUG, AND OF THF ACADKMY 



OF 8CIKNCE3 OF FUILAUELPiriA, A>D OF THE ROYAL ACADEMY OF SCIKIVCES 



OF TURIN ; FOREIGN M E M 1) R K OF THE KOYAl. SOCIETY OF SCIENCES OF 



GOTTINGEN, AND OF THF, .11 O Y A I. BO H KMT A N SOCIETY OF SCIENCES , AND 



OF THE ACADEMY OF THE M.NCEI OF ROME, AND OF THK AMERICAN 



ACADEMY OF ARTS AND SCtENCKS OF BOSTON ; ASSOCIATE OF THK 



BOYAl. ACADEMY OF BELGIUM; HONDRARY MEMBER OF THK 



NEW YORK ACADEMY OF SCIENCES, AND OF THK 



CAMBRIDGE PHILOSOPHICAL SOCIETY, AND OF 



THK KOYAI. PHYSICAL SOCIETY OF EDIN* 



BtTRGH, AND OF THK 



BIOLOGICAL SOCIETY OF PARIS, AND OF THE CALIFORNIA ACADEMY OF SCIENCES OF SAN FRANCISCO, A N Ii 



OF THE ROYAL ZOOLOGICAL AND M A L ACOLOGIC A L SOCIETY OF BELGIUM; 



CORRESPONDING MEMBER OF THE SENKKNBERG ACADEMY OF FR AN KFURT-A" M ; 



FOREIGN ASSOCIATE OF THK NATIONAL ACADEMY OF SCIENCES, U.S.. AND MEMBER OF THK 



AMER "AN PHILOSOPHICAL SOCIETY ; 



HONORARY FELL(_ .V OF THE ROYAL SOCIETY OK EDINBURGH; 



LATE lUKKCTCHt OF THE NATURAL HISTORY DEPARTIMKNTS OF THK BRITISH MUSEUM i LATE PRESIDENT OF THE 



BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCK; LATE FULLKKIAN PROFESSOR OF 



PHYSIO LOGY IN THE UoYAI. INSTITUTION OF GREAT BRITAIN; 



LATK LINACBE PROFESSOR OF COMPARATIVE ANATOMY AND FELLOW OF MKRTON C OLl.E GE , OX FO R D ; 



EMERITUS PROFESSOR OF ZOOLOGY AND COMPARATIVE ANATOMY IS UNIVERSITY COLLEGE, UNIVERSITY OF LONDON 



WITH THE CO-OPKKATION OF 



ADAM SEDGWICK, M.A., F.R.S., 



rELLOW OF TRINITY COLLEGE, CAMBRIDGE. AND PROFESSOR OF ZOOLOGY IN THE IMPERIAL COLLEGE OF 



SCIENCE AND TECHNOLOGI, LONDON; 



SYDNEY J. HICKSON, M.A., F.R.S., 



iSSOR OF ZOOLOGY IN T H IC UNIVERSITY OF M, 



E. A. MINCHIN, M.A., 



BF.YKR PROFESSOR OF ZOOLOGY IN T H IC UNIVERSITY OF MANCHESTKR; 



PROFESSOR OF PROTOZOOLOGY IN THE UNIVERSITY OF LONDON; 



AND 



GILBERT C. BOURNE, M.A., D.Sc, F.R.S"., 



LINACRE PROFESSOR OF COMPARATIVK ANATOMY, AND FKLLOW OF MERTON COLLEGE, OXFORD. 



WITH LITHOGRAPHIC PLATES AND TEXT-FIGURES. 



LONDON. 

 J. & A. CHCJECHILL, 7 GREAT MARLBOROUGH STREET. 



1910. 



Adlard and Son, Impr.,] 



[London and Dorking. 



