Miscellaneous. 245 



the expense of the length. The bulb shows through the thin inte- 

 gument, and without close examination may be taken for a third 

 orifice. The penis is perforate, and has a dilated cavity within the 

 bulb. Immediately above the penis I indistinctly observed a some- 

 what lobated organ, which appeared to join the penis at its base by 

 a narrow portion. This is probably the testicle, for it was the only 

 thing I could discover in connection with the genitalia to correspond 

 to it. 



In two individuals only could I see part of the female organs. This 

 consisted in two sigmoid tubes or oviducts, which could be traced 

 from the generative orifice a short distance forwards, one on each 

 side of the penis. 



I could detect no traces of a nervous system. 

 The eyes, so called, have been previously described. It is still a 

 question with many, whether these, as well as the corresponding 

 deep black points existing in very many of the lower animals of the 

 invertebrate series, subserve the purpose of eyes ; and some anato- 

 mists have even gone so far as to deny the sense of sight to the 

 comparatively perfect eye of many gasteropodous mollusca. The 

 experiments which are made to test the existence of this sense in 

 these organs for the most part are exceedingly fallacious, generally 

 being performed by concentrating the light upon them through a 

 lens. Insects, and even serpents and frogs, I find will frequently 

 bear the impression of a sudden glare of light produced in this way 

 •without any inconvenience, at other times they will seek to avoid it ; 

 but Helix albolabris will occasionally retract its tentacle when so 

 disturbed, and Phagocata will frequently raise its anterior extremity 

 and move from the too great light. From their position, which is 

 always such as to be well exposed to the influence of the light ; from 

 their structure, imperfect as it is in many cases, and their connec- 

 tion with the nervous system when this exists, I am led to conclude 

 that in all cases they are organs of vision. 



The general sensibility of Phagocata is very considerable, that is, 

 it contracts with great readiness from the slightest disturbance. The 

 contraction has much the appearance of being involuntary, and is 

 very like that of the Medusce. When an individual is irritated at 

 any point, contraction commences there, and thence rapidly extends 

 throughout the animal, and the only appearance of volition is in the 

 effort to escape ; but if the touch be too rude, apparently involuntary 

 contraction takes place suddenly, and appears to destroy all ])ower of 

 volition for the moment ; the animal however soon revives from this 

 state and glides off with its accustomed speed. 



Some experiments which I performed upon Phagocata confirm the 

 statements that the Planarice are capable of repairing injuries. When 

 aa individual is cut into two, both parts after a time become distinct 

 and perfect animals. Division carried to a greater extent in some 

 instances results in as many perfect animals as there are parts, but 

 generally I have found that when cut into more than three or four 

 pieces, the intermediate pieces are apt to die, and sometimes the ex- 

 tremities do not survive. — Proc. Acad. Nat. Scien. Philadelphia. 



