J.«N 23 ISIS 
7«7 
New Series. No. 248 (Vol. 62. Part 4i. Price 10s. 6d. net 
Subscription per volume (of 4 parts) 42s. net. 
DECEMBER, 1917. 
THE 
QUARTERLY JOURNAL 
OF 
MICROSCOPICAL SCIENCE. 
RDITKI) H Y 
Sir RAY LANKESTER, K.C.B., M.A., D.Sc., LL.D., P.R.S., 
HONORARY KK1.LOW O K KXKlKR COI.LKGK AND HONORARY STUDENT OF CHRIST CHURCH, OXFORD; 
MEMBER OF THK INSTITUTE OF FRANCK (ASSOCIE ETRANGER DE l’aCADEMIE DES SCIENCES); 
COR RICS PON DENT OF 1 II It IMPERIAL ACADEMY OK SCIENCES OF ST. PETERSBURG, AND OF THK 
ACADEMY OK SCIENCES OF PHILADELPHIA, AND OF THE ROYAL ACADEMY OF SCIENCES 
OF TURLN ; FOREIGN MEMBER OF THK ROYAL SOCIETY OF SCIENCES OK 
GOTTINGEN, AN1) OF T II F. ROYAL BOHEMIAN SOCIETY OF SCIENCES, A N D 
OF THE ACADEMY OF THE I.INCKI OK ROME, AND OF THE AMERICAN 
ACADEMY OF ARTS AND SCIENCES OF BOSTON ; ASSOCIATE OF TDK 
ROYAL ACADEMY OF BELGIUM. HONORARY MEMBER OF THE 
NEW YORK ACADEMY OF SCIENCES, AND OF THK 
CAMBRIDGE PHILOSOPHICAL SOCIETY, AND OF 
THE ROYAL PHYSICAL SOCIETY OF EDIN- 
BURGH, AND OF THK 
BIOLOGICAL AND ZOOLOGICAL SOCIETIES OK PARIS, AND OF THE CALIFORNIA ACADEMY OF SCIENCES OF 
SAN FRANCISCO, and OF THE ROYAL ZOOLOGICAL AND M AL ACOLOGIC A L SOCIETY OF BELGIUM; 
CORRESPONDING' MEMBER OF THE SKNKENBEKG ACADEMY OF FRANKFURT A MJ 
FOREIGN ASSOCIATE OF THK NATIONAL ACADEMY OF SCIENCES, U.S., AND MEMBER OF THE 
AMERICAN PHILOSOPHICAL SOCIETY ; 
HONORARY FELLOW OF THE ROYAL SOCIETY OF EDINBURGH*, 
LATE DIRECTOR OF THE NATURAL HISTORY DEPARTMENTS OF THE BRITISH MUSEUM; LATE PRESIDENT O F THE 
BRITISH ASSOCIATION FOR THE ADVANCEMENT OF SCIENCE,* LATE KUI.LKHIAN PROFESSOR OF 
PHYSIOLOGY IN THE ROYAL INSTITUTION OF GREAT BRITAIN i 
LATE MNACRK PROFESSOR OF COMPARATIVE ANATOMY AND FELLOW OF M1CRTON COI.I.KGlt, OXFORD; 
EMERITUS PROFESSOR OF ZOOLOGY AND COMPARATIVE ANATOMY IN UNIVERSITY COLLEGE, UNIVERSITY OF LONDON 
WITH THE CO-OP Jfi RATION OF 
SYDNEY J. HICKSON, M.A., F.R.S., 
BEYER PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF MANCHESTER; 
HILBERT C. BOURNE, M.A., D.Sc., F.R.S., 
CSSOIt OF COMPARATIVE ANATOMY, AND FELLOW OF MERTON COLLEGE, OXFORD 
J. GRAHAM KERR, M.A., F.R.S., 
I.I * ACRE PKOFHSSO K 
REGIUS PROFESSOR OF ZOOLOGY IN THE UNIVERSITY OF GLASGOW; 
AND 
;. W. MAC BRIDE, M.A., D.Sc., LL.D., F.R.S. 
PROFESSOR OK ZOOLOGY AT THE IMPERIAL COLLEGE OF SCIENCE AND TECHNOLOGY. 
WITH LITHOGRAPHIC PLATES AND TEXT-FIGURES. 
LONDON: 
J. & A. CHURCHILL, 7 GREAT MARLBOROUGH STREET. 
1917. 
S 
Adlard & Son & West Newman, Ltd.,] 
[London and Dorking. 
