MICROHYDRA DURING I907. 95 



the overgrowth of Pohv.oa, etc., during the time required to 

 perfect its organism, while forming a capitiihun and terminal 

 mouth at one end and attaching the other by a pedal disc to 

 the same surface that has supported the parent. If, however, 

 its starting point in life has been upon the overhanging edge 

 of a stone, we may often see the liberated larva hanging from 

 it by an invisible thread, probably of mucus, until a momen- 

 tary current in the water of our culture jar drifts it against 

 the glass, where by the same suffusion it is held slightly, 

 while traveling evidently but invisibly, if the expression may 

 be allowed, during its larval growth into a state of ability to 

 feed and nourish itself; when a pedal disc becomes requisite. 



AS SERN I^PON THE SIDES OF A JAR. 



We here have it in one of the positions suggested for 

 examination — not ideal, of course ; — the glass is cun^ed and 

 of uneven thickness ; reflected light must come through 

 another cun^ed surface with six or more inches of impure 

 water intervening ; the supporting base of the hydroid also 

 intervenes between our lenses and the branches, whose struc- 

 ture and contents we want to examine ; these are, of course, 

 frequently turned directly inward and away from our lenses ; 

 and, worse perhaps than any other, impurities may lodge 

 upon the mucous coatings of the hydroid and hide what we 

 might otherwise see ; but it is the best we can contrive until 

 some one designs small aquaria with iiat, smooth sides, with 

 which we can replace our culture jars. If these could be 

 secured of such dimensions that they could be used upon the 

 stage of our microscopes or in front of them, we should be 

 content. At present we have to study our friends where they 

 place themselves, in common jars, not fruit jars, but what are 

 far better, candy or confectioners' jars (often called specie 

 jars), — and then build up a " microscopic obsei^vatory . " A 

 description of this may be allowed. Removing the mirror bar 

 with its substage fixtures from our instrument we bring down 

 the tube into a horizontal position and run the objective in 



