594 MALCOLM LAURIE. 



two chelicerse are twisted so that the chitinous plates come into 

 contact with each other, leaving a small hole (fig. 16, co) 

 through which the cord of cells passes to the mouth. I think 

 it is probable that the chelicerae do not merely hold the cord 

 in position, but serve also to crush it. The lower end of the 

 cord consists of horny-looking cell-walls from which all the 

 protoplasm seems to have disappeared. Whether the embryo 

 nourishes itself on the protoplasm of the cells or whether the 

 cell contents are some special substance I have not been able 

 to find out. It is perhaps worthy of remark that the chitinous 

 plates on the chelicerse are covered in places with a scale-like 

 marking very similar to that which is so characteristic of 

 the fossil Merostomata. The epistomial lobe (figs. 16 and 

 17, est) is very well developed, and also furnished with chitinous 

 plates. 



The five succeeding pairs of appendages closely resemble 

 their adult state, and need no description here. 



The genital opercula are in my latest stage not yet visible 

 in a surface view, contrasting in this respect with the pectines 

 (fig. 15, vii). 



The six metasomatic or caudal segments present one point of 

 interest in Sc. fulvipes, namely, that the tail is bent up over 

 the back, contrasting in this respect with Euscorpius, in which 

 the tail lies along the ventral surface. 



From what I was able to make out as to the development 

 of the median eye, I think that the pigment-cells are epi- 

 blastic. The retina of the eye is formed, as in Euscorpius, from 

 a thickening of the dorsal wall of the cerebro-optic invagina- 

 tion. The thickened portion consists at first of a mass of 

 large spherical nuclei, which are distributed through the whole 

 thickness of the retina. In the latest stage which I examined, 

 in which there is already a considerable quantity of pigment, 

 the nuclei are confined to the inner half of the retina, leaving 

 the outer portion quite clear (fig. 18). The nuclei are, how- 

 ever, no longer all alike; but, while the majority of them retain 

 their spherical form, a certain number, forming a band in the 

 middle of the retina, have assumed an elongated form. These 



