98 Rev. F. O. Pick:u(l-Caiubrid;re on 



Dr. Meade's collection : 



1. A.Momen diill, unicolorous; no spines on 



metatarsi. From coal-pits P. Meadii, 1*. Lb. 



2. Abdomen olive-green ; spines on metatarsi . P. erram, BL 



Mr. Campbell's collection : 



1. Abdomen dull ; no metatarsal spines .... P. Meadii, F. Cb. 



2. Abdomen olive-green ; spines on metatarsi . P. errans, Bl. 



Mr. Blackwali's types : 



Abdomen olive-green ; spines on metatai'si . P. errans, Bl. 



Rev. 0. P. Cambridge's collection : 

 Examples of both species. 



There is now the further question as to the identity of 

 P. ohlongcij Cb., with P. errans^ Bl., or the distinctness of 

 them as different species. Mr. Campbell liad been greatly 

 puzzled, when examining his specimens, by the real or appa- 

 rent variation in the position of the eyes in specimens which, 

 judging by other characters, might have been regarded as the 

 same species. 



After much careful examination my own conclusion is 

 this : that though it is not at all improbable that there may 

 be considerable instability in the position of the eyes even 

 amongst spiders otherwise similar, and though I have been 

 compelled during my arachnological studies, as have many 

 others before me, to conclude that such is really the case, and 

 that in all probability the forms have not yet become fully, 

 ultimately, and specifically differentiated, yet that, with 

 regard to these particular examples, such a view is not wholly 

 tenable. 



I have no hesitation in saying that the apparent difference 

 in the distances between the eyes is due in a vast number of, 

 perhaps all, cases to the shrinking and falling away of the 

 tissues and pigment-cells from the exoskeleton. 



According to my experience this always has the effect of 

 exhibiting the outline of the lenses of the eyes more distinctly, 

 and making them appear further apart than when the pig- 

 ment-cells are present. For instance, the eyes of a pale, 

 young, diaphanous specimen always appear further apart than 

 those of one in which the pigment-cells are rich and well- 

 developed; and if the eyes of a cast-off cephalothoracic 

 skeleton be compared with those of one in the normal con- 

 dition, the truth of this statement will be perceived. 



And although I am prepared to maintain tiiat, amongst the 

 smaller species at any rate, specific characters constantly melt 



