Alir,iiST. 1911. 



KNOWLEDGE. 



299 



Willi gHin,^ 

 closinj; 





\\a\- when the vesicle contracts, and tlun 

 This alternating action seems to 

 serve a respiratory purjiose. 

 the water thus taken in and 

 expelled being distributed 

 - through a ss'stem of channels 

 and vacuoles excavated in 

 the substance of the body, 

 some of the vacuoles which 



vacuoles 

 are nearest the surface being 



Figure 1. 



observed to undergo disten 

 tion when the vesicle con 

 tracts, and to empty themselves gradually 

 as it refills." 



When injured in an\- wa\' the recupera- 

 tive power of the Actinosp/uicriiiiii appears 

 to be very great. It sometimes happened 

 that on transferring a specimen from the 

 aquarium to the glass cell for purposes of 

 examination the organism would sustain 

 more or less damage, and on one occa- 

 sion so great was the injury that a con- 

 siderable portion of the endoplasm was 

 pressed out of the bod\- and could be 

 seen floating in the surrounding medium, 

 while the pseudopodia were all more or 

 less destroyed. Despite, however, these 

 apparently hopeless injuries, the work of 

 repair was at once commenced and so 

 quicklv effected that in a comparativeh' 

 short space of time the Actiiwspliacriimi 

 had made good the damage sustained, 

 and with extended pseudopodia was ready 

 to seize any prev that might happen to 

 cross its path. 



It is generalh- stated that w hen unsuit- 

 able conditions arise, the Actiuosphacriuiii 

 becomes encvsted, remaining in this con- 

 dition until the provision of a more favour- 

 able environment enables the organism to 

 resume its normal state of existence. 



No doubt this is sometimes the case, 

 \et close observation points to the fact 

 that under unsuitable conditions death 

 often supervenes, while encystment more 

 generally takes place prior to reproduction 

 by division. 



Previous to death the endo[ilasm becomes greatl\- 

 contracted and numbers of the pseudopodia appear 

 to fuse, a process which gives them the appearance 

 of broad spikes protruding from the body. After 

 remaining in this condition for some time the 

 contents of the body break through the containing 

 membrane at some one point, filling the surrounding 

 water with globules of various sizes. 



A large portion of the life of the Acfinosp/uicriiiiii 

 appears to be occupied with the capture of food, the 

 choice ranging from small particles of vegetable 

 matter to free-swimming infusorians, and even such 

 comparatively highly organised and powerful 

 creatures as the various species of Entomostraca. 

 Of these latter the smaller species are easily 



captured, eaten, and digested, but with the larger 

 species the Acfiiiospluieriiiiii does not appear 

 powerful enough to deal. 



The organism appeared also quite unable to cope 

 w ith some Paramecia when placed in the same cell ; 

 the infusorians by a sudden twist of the body 

 speedily freeing themselves from the clutches of the 

 pseudopodia, which latter were invariably much 

 damaged, and not unfn-iiucntly completely torn off 

 in the struggle. 



Periods occur when the Actinosphacrium rests 



fr 



the 



Figure 2. 



Figure 3. 



Figure 4. 



abour involved in securing a sufficient food 

 supplv, and it is of great interest to note 

 that during these intervals free-swimming 

 infusorians appear able to come into 

 contact with the pseudopodia with no 

 danger ensuing to themselves. 



When food-taking, the method adopted 

 bv the Actinoftpliaeriiim for capturing its 

 prey is of peculiar interest. 



Should an infusorian or other organism 

 chance to come into contact with one of 

 the pseudopodia, it is at once captured 

 and firmly held ; the capture being 

 generallv attributed to the action of a 

 coating of some viscous substance. If 

 this be really the correct solution, it 

 seems clear that this substance can be 

 secreted only during such time as the 

 Actiiiosphacriiiiu is engaged in food-taking; 

 for, as previously mentioned, there cer- 

 tainlv occur periods when similar organ- 

 isms are able to come into contact with 

 the pseudopodia with perfect impunity. 



In the event of the captured organism 

 proving to be of small size, it glides up 

 the pseudopodium until, on reaching the 

 bod}-, a portion of the ectoplasm appears, 

 as it were, to be rolled back, thus forming 

 a kind of mouth within which the strug- 

 gling victim is speedih" engulfed. 



When, however, an Entomostracan 

 or other comparativeh' large organism 

 happens to be caught, the mode of 

 procedure adopted 

 bv the Acfiiio- 

 sphdcriiiii! appears 



to be of a different character. 



In such a case the neigh- 

 bouring pseudopodia are bent 



over to assist in holding the 



captured prey, while, by a 



process of contraction, the 



latter is slowly conveyed 



towards the body of the 



Actiiiosphaeriiim. After being 



engulfed, the Entomostracan 



or other organism is seen to 



be enclosed in a vacuole 



which soon commences a 



slow circulation round the 



body, a considerable time. Figure 5. 



