1884.] NATURAL SCIENCES OF PHILADELPHIA. 19 



minutes, when both were lost to sight among a mass of sediment, 

 and the fear of mistaking one of the common monads for them 

 led the observer to abandon the search. Returning to the parent 

 capsule, a third monad was found to have escaped in the mean- 

 time. After twenty-four minutes quiescence, the fourth body in 

 its turn approached the wall of the capsule, emerged, developed 

 a flagellum, and swam away, a free monad. With a one-half 

 inch objective this one was closely watched, and the following 

 details noted: bod3'^ oval, transparent; nucleus present, dark- 

 colored and situated near the centre ; a pulsating pink vesicle, 

 situated posteriorly ; and a flagellum slightly longer than the body. 



For one hour and fifty-eight minutes the monad swam in all 

 directions, usually in concentric, ever widening circles, then 

 suddenly darting off at a tangent to begin again in a new spot. 

 At the end of this time, in its course it touched one of the free 

 young Clathrulina, and, to prevent it being used as food by its 

 cannibal relation, the glass cover of the live-box was tapped, so 

 that the current produced carried the monad a short distance 

 away, where it remained almost motionless several seconds. 



B}' a change to a power of three hundred and fifty diameters, 

 the monad was shown to attach the top of its flagellum to the 

 glass and revolve swiftly for a few moments, when instantly the 

 whole body became spherical, rays were shot out, and the trans- 

 formed monad was in no point, except that of size, to be distin- 

 guished from its Actinophrys-like cousin, whose career had been 

 so diff'erent. In some cases the monads remained attached by 

 the flagellum, using it as a pedicel. The whole development, from 

 the time when the monad began its free life, occupied two hours 

 and some seconds. 



This mode of reproduction secures a more widespread distri- 

 bution of the young than would be possible did this depend on 

 the sluggish Actinophrys form. It seems reasonable to suppose 

 that this is a wise provision for the perpetuation of the species, 

 should adverse conditions of life arise;. and also to prevent an 

 undue accumulation of the animals within a circumscribed space. 



The tendency of these rhizopods to attach themselves to the 

 parent capsule, a result of the inertness of the Actinophrj^s form 

 of young; together with the fact that this mode of reproduction 

 was apparentl}' induced by a lengthened captivity, necessarily 

 the source of adverse conditions, would point to the reasonable- 

 ness of the above conclusions. 



