LIFE-CYCLE OF " CYSTOBLV " IRREGULARIS (mINCH.). 9 



sporidia is it of the slightest use so far as nuclear detail is 

 coucerued. 



Special effects of fixatives or stains on different structures 

 will be mentioned when dealing- with them in detail. 



(c) Attempts at artificial infection. — I endeavoured 

 to keep the Holothurige alive in the aquarium, but from 

 some cause or other they would not settle ; it may have been 

 owing to the great difference between the pressure in the 

 tanks and that to which they are accustomed in their natural 

 surroundings. Invariably after a short time the skin became 

 broken and patchy, shovv'ing evident signs of maceration, and 

 this was the sure prelude to general evisceration. ^ The 

 animals were always kept quite separate from anything else 

 likely to injure them, so the ill-health was not the result of 

 being bitten. For this reason alone the pi'ospect of successful 

 infection and of obtaining early stages of the parasites 

 appeared to be very doubtful. When, moreover, I came to 

 try it, I soon found artificial infection at all to be a most 

 difficult matter. 



It was necessary to actually convey the cyst containing 

 spores inside the Holothurian's mouth, not only to be certain 

 that the animal really swallowed the spores, but also to know 

 approximately the time, in order to have any chance (by 

 killing the animals after different intervals) of subsequently 

 observing the liberated sporozoites and their passage through 

 the gut-wall. A Holothurian's mode of eating is to sweep up 

 particles of sand, shell, etc., with Avhatever organic material 

 may be amongst them, from the surface on which it happens 

 to be crawling by means of its tentacles. These, of the 

 Aspidochirote type, are furnished with an expanded, bi'ush- 

 like, distal end to which the particles adhere. The tentacles 

 are in turn stuffed into the mouth and then withdrawn, the 

 food having been sucked up into the oesophagus. 



I could not trust to such a haphazard method as this 

 with much likelihood of success, so I endeavoured to feed 



' Ludwig (24) mentions tliis curious fact, saying that, after irritation, " die 

 Haut sicli ziemUcli rascli in fonnlosen Schleim auliost." 



