114 PLANAEIA. 



Only the head of fig. 11 survived mutilation, also on September 14 ; 

 it had become nearly symmetrical on October 24, by acquiring a new tail. 

 But the brown colour of the original was now converted to grey, fig. 16. 



Of a third specimen, subdivided into three portions, all had become 

 entire and nearly symmetrical animals in twenty-eight days. The middle 

 portion had regenerated both a head with its two eyes, and a tail. The 

 lowest section had regained a head and eyes ; and the highest, preserved 

 by its ova, had acquired a tail. Thus the more prominent parts of the 

 external organization were multiplied from the original two to six, by 

 experiment. Fig. 17, head, with a regenerated tail ; fig. 18, middle sec- 

 tion, regenerating both head and tail ; fig. 19, tail, having regenerated a 

 head. 



That similar redintegration would restore the integrity of mutilated 

 animals, I had ascertained many years ago. These observations, together 

 with the skilful and successful experiments of Dr James Rawlins John- 

 son, render the farther prosecution of the subject, to which I personally 

 feel peculiarly averse, altogether unnecessary. 



These PlanariiB dwell in springs or fresh-water rills, under stones, or 

 involved in leaves. They are exceedingly sensitive of atmospherical al- 

 terations. When the thermometer fell suddenly from G5 to 56, they 

 scarcely continued moving. 



Though numbers inhabited the well above specified, and a rill at a 

 short distance from it, none could be found in a pond within 100 yards 

 of the former. Several of the lower tribes, however, abounded there. 



Desirous of ascertaining what changes might have taken place 

 among these animals after an interval of twenty-five years, whether in 

 aspect or properties, I took some from the same spring-well that had 

 formerly supplied rne in Linlithgowshire. Now, I hardly recognise the 

 precise spot from the numerous changes the neighbourhood had under- 

 gone. But the appearance of the animals I succeeded in procuring was 

 the same, chiefly slate-grey, of various intensity, a few brownish. Food 

 seemed very scanty in their vicinity. The details of my purposed object 

 were accidentally defeated. 



