Cristatella. Z. ASCIDIOIDA.- 309 



in diameter, formed as a horse-shoe, and bordered by a hundred ten- 

 tacula. Towards one side the mouth, of singular mechanism, seems to 

 have projecting- lips and to open as a valve, which folds up within, con- 

 veying the particles which are absorbed to the wide orifice of an intes- 

 tinal organ which descends, perhaps in a convolution, below, and re- 

 turns again to terminate in an excretory canul under the site of the 

 tentacula. Probably the whole race of Cristatellse is distinguished by 

 a similar conformation." 



" The polypus is a very vivacious animal, quickly retreating for 

 security when alarmed, and rising to expand in activity. Though 

 each be endowed with independent life, sensation, and all the motions 

 that can be exercised without actual transition, the whole are sub- 

 jected to the volition of the sluggish mass in respect to progression : 



— they arc borne along with it." " A specimen having been cut 



transversely asunder, each portion seemed to recede by common 

 consent ; but both survived, as if sustaining no injury. Neither is 

 any polypus affected by the violence offered in its vicinity. 



" Twenty, thirty, or more lenticular substances, of considerable 

 size and in the most irregular arrangement, imbedded in the flesh, 

 are exposed through the translucent green of the animal. Its death 

 and decomposition towards the end of autumn liberate them to float 

 in the water. Subjected to the microscope, or, indeed to the naked 

 eye, their convex surfaces prove brown, the circumference yellow, 

 and begirt with a row of spines terminating in double hooks. Each 

 is an ovum of the Cristatella with a hard shell, and occupied by yel- 

 lowish fluid contents." " In 3 or 6 months the ovum gapes at 



one side to allow the protrusion of an originating polypus, which by 

 a remarkable provision of nature now floats reversed, with the head 

 downwards, to ensure absorption of the liquid element below. On 

 quitting the ovum it attaches itself to some solid substance by the 

 base, then disproportionately large, from which a second polypus 

 quickly rises, then a third, and a fourth ; and thus with others. In 

 earlier stages the Cristatella mirabilis seems to be of a circular figure, 

 and in its most mature state there is a margin projecting beyond 

 the root of the polypi." Dalyell. 



To illustrate this description of Sir J. G. Dalyell, the only 

 naturalist who has observed the species in Britain, I have given 

 copies of the beautiful figures of M. Turpin in Plate xliii, for 

 there can surely be scarce a question of the identity of the 

 continental and British zoophyte. Turpin's figures, it is to be 

 noticed, were drawn from young or slightly developed specimens ; 

 a mature polypidora with its 300 individuals must indeed present 



