132 Dr. G. C. Wallich on the Value of 



surface unprotected. Such a view is therefore untenable ; and, 

 as I have endeavoured to show, the appearances are only recon- 

 cilable with one or other of the following processes : that is to 

 say, the food-particle, on being dragged to the surface, or sur- 

 rounded, as the case may be, either penetrates the ectosarc and 

 finds its way into a cavity extemporized in the endosarc, or, the 

 cavity being formed partly by the inversion of a portion of the 

 ectosarc, which is thrust in, as it were, before it, the sealing up 

 of the food-vacuole is effected by a portion of endosarc. In the 

 first case, the mere contact of the endosarc with the portion of 

 water which is admitted along with the incepted object converts 

 it into ectosarc. In the second, that part of the food-vacuole 

 which does not already consist of ectosarc is converted into it 

 by the same means. But under no circumstances have the 

 appearances been such as to lead me to the inference that the 

 food object passed into the interior in the same manner that a 

 stone does when slowly dropped into water. 



It might, at first sight, be imagined that the food-vacuole is 

 a simple cavity produced within sarcode by the presence of a 

 foreign body, after the fashion of a globule of oil in water, since 

 the incepted masses at times present no appreciable vacuolar 

 space around them; or that the endogenous vacuolation, to 

 which reference has been made, negatives the above view. To 

 the first of these objections I would answer that the vacuole, 

 when present, undoubtedly contains watery fluid ; and it appears 

 almost certain that a distinct coagulative effect is produced in 

 the endosarc by contact with it, from what takes place when 

 effete matter is extruded through a tubule in the neighbourhood 

 of the villous organ. AVe then perceive that, on reaching this 

 region, the contractile power is so great as to cause the vacuole 

 and its contents to move towards the margin, and the egress of 

 the effete matter proceeds slowly till its largest diameter has 

 passed outwards. When this has happened, the effete object 

 slips out with a jerk, whilst the residue of the contractile effort 

 causes the vacuolar spherule to assume a tubular and, very fre- 

 quently, an infundibuliform shape, similar to that described and 

 figured by me in the 'Annals' for May. But at this point the 

 special contractile effort ceases, and hence the consoUdated layer 

 constituting the wall of the tubule requires a considerable pei'iod 

 for its reconversion into endosarc, which proceeds from within 

 outwards. In this case, it is very evident, I think, that, did no 

 difference exist between the degree of consolidation of the tu- 

 bular wall and the endosarc by which it was immediately sur- 

 rounded, the reconversion spoken of, and the consequent obli- 

 teration of the excretory tubule and its external oritice, would 

 be comparatively instantaneous, instead of occupying, as it ge- 



