MICROHYDRA DURING I907. 93 



down the canal. Here, at a depth of six feet or more, a 

 violent current prevents the accumulation of much silt upon 

 the stones and at the same time supplies the favored tenants 

 with an abundance of food. 



COLLECTING. 



It is no trifling labor to dredge up and recover these stones 

 from the depths mentioned, working from an unstable boat in 

 the last named violent current. The one consoling fact is 

 that we may be positively certain of our game. Seldom 

 indeed is a stone brought up that is not literally covered with 

 life in various forms, Polyzoa, Annelids, Hydroids, Rotifers, 

 etc. I should be " de-lighted," as somebody says, to have other 

 localities of equal promise pointed out to me, for there also, I 

 think, might be found M. ryderi. It is desirable to gather 

 many small, thin stones that may be examined in shallow 

 dishes with just sufficient water to cover them, and to pay 

 particular attention to their margins, where the capitido' are 

 often stretched out so as to be illuminated by transmitted 

 light from the mirror below. By an occasional syringing of 

 the surface we may see many other forms b}^ direct light ; but 

 it is difficult to reach them with high powers without undue 

 risk to our lenses. 



DESCRIPTION OF A-SEXUAL MULTIPLICATION. 



The difficulty, or one great difficulty, in studying the life 

 history of this organism seems to lie right here : — As it is not 

 a free swimmer (in its earh'- condition ) it cannot follow its 

 prey ; and without tentacles it cannot even reach after it 

 effectively and control its victim, without establishing a firm 

 base of support. This, under natural circumstances, is found 

 upon rough stones as described, where it is protected and 

 somewhat hidden from sight of the animals it would catch ; 

 who thus crawl over it, unsuspicious of danger, and are para- 

 lyzed and caught unawares. From these rough places it can- 

 not be removed without violence, and it remains yet undeter- 



