18 On the Encystment o/^Eolosonia. 



that all the cocoons, eacli funiislied with its one ovum, were 

 fabricated either upon the same day or at the exact intervals 

 that would allow of the embryos simultaneously reaching 

 their full term of development. This supposition is rather 

 too much to believe. Fourthly, the supposed cocoons possess 

 no apparatus of fixation ; this is not a positive bar to believing 

 them to be cocoons, for some worms have not any such 

 mechanism, but in others the cocoon is enveloped in a gelati- 

 nous layer which causes it to adhere firmly to the surface 

 upon which it falls. Fifthly, and, if my observations arecorrect, 

 this is an absolute and final objection to regarding the cysts 

 of jFoIosoma as cocoons. I treated a number of these bodies 

 with strong potash; the first effect of this reagent was to 

 change the colour of the pigment to a splendid violet, which 

 rapidly disappeared. This fact I have already recorded in 

 this Journal*. The second effect was to colour bright green 

 the contents (be it noted that there icere contents) of the ali- 

 mentary canal. jEolosoma is a vegetable feeder, and potash 

 produces a precisely similar effect upon the colouring sub- 

 stances of various algte. The natural inference is that the 

 supposed embryos had been feeding upon such algaj ; clearly 

 therefore they cannot be embryos at all, as algaj could not 

 gain access to the interior of the cysts. They must have fed 

 upon these algJB and then encysted themselves. It is perhaps 

 unnecessary to state that the worms within the cysts had 

 set£e precisely similar to those crawling about outside. I 

 mention this fact, however, more ))articularly since Maggi did 

 not find seta^ upon the worms within the cysts described by 

 him. The setaj might, however, be passed over ; they are 

 extremely delicate, and the position of the worm in the cyst 

 — coiled upon itself — is not by any means a favourable one 

 for allowing these structures to be seen. 



Considering all these facts it seems to me necessary to 

 arrive at the conclusion that yFolosoma can temporarily encyst 

 itself, after the fashion of some of the lower organisms. It 

 should be noted that the alimentary tracts of the free-swimming 

 individuals did not for the most part contain much food ; and 

 I saw but little evidence of active feeding on the part of the 

 worms in the shape of the very characteristic pellets of dung 

 evacuated by these Annelids, This cessation of feeding may 

 be preliminary to encystment; tiie torpor caused by the 

 approach of winter may have brought about a general cessa- 

 tion of activity, ^^ Inch culminates in encystment tor a period 



• "Notes upon cortaiu SjH'cies of .T'.ohsoimi ," Ann. ,<: Majr. Nat. Hist. 

 Oct. 1889. 



