f>4 



OHSEP.VATIOXS OX FH-Altl.TC. 



communications — seeks to overthrow this theory. In the interests 

 of science it is desirable to publish the facts forming tlie basis of 

 this midiilj warm controversy, in which Dr. Magalhaes has certainly 

 the best of the argument. So far as my own observations have 

 gone, it seems pretty clear that neither Dr. Magalhaes, nor Dr. 

 Paterson, nor even Dr. Lewis himself, appears to have correctly 

 interpreted the nature of this envelope. Dr. Lewis has persisted all 

 along in calling the structure in question " a sheath." It seems to 

 have escaped the knowledge of almost all observers that the so- 

 called involucrum is neither more nor less than an ordinary skin- 

 cast, such as invariably accompanies the moultings of nematode 

 worms. Different larval nematodes cast their skins at dijBferent 

 times, and this moulting is usually accompanied with an alteration 

 in the form and structure of the larva, involving the loss of the 

 original tail. 



T. Spencer Cobbold. 

 February 26th, 1880. 



APPENDIX. 



Eemarks of the Local Migration of Micro-filari.e. 



By J. Mortimer-Granville, M.D. 



Assuming that the change of locality is found to be habitual, and 

 that it is not a too hasty generalisation from insufficient data, it 

 will, I believe, be of great value to the student of rhythmical 

 phenomena like that of '' sleep." The change of place may be 

 fairly ascribed to change of state. Looking to the habits of life in 

 the lowest organisms, it can scarcely be supposed that the periodicity 

 can depend on the state or requirements of the Filarice. It is not 

 likely that the parasite needs repose, or that it resorts to special 

 localities to feed. It seems more probable that the state of the 

 circulating fluid determines the presence or absence of the Filarice in 

 its main current, by night and day respectively, or during the 

 waking and sleeping states. Your verbal account of Dr. Manson's 

 report is not quite explicit as to whether the change oj locality 

 depends on sleep)', or siinply the advent of night. The alterations and 

 alternations of condition which takes place in the blood are three 

 (perhaps four) in number, so far as any living organism present in 

 it is concerned. 



