420 Dr. A. Strubell on the 



At tlie period of ovlposition the female Thelyphonus buries 

 itself fairly deep, often as mucli as a foot and more, in the 

 earth, and there lays its eggs. Simultaneously with these 

 tliere issues from the genital aperture a secretion which 

 speedily hardens in the air and surrounds the eggs in the 

 form of a thin-walled transparent sac. This is attached to 

 the ventral surface of the animal, and contains a variable 

 number (fifteen to thirty) of ova. 



The ovum, which is oval in shape and rich in yolk, is of 

 the considerable size of nearly 3 millim., and is surrounded 

 by a chorion of a yellowish colour, to which a delicate vitel- 

 line membrane is closely attached. 



After the formation of the blastoderm there appears near 

 one pole of one side of the ovum, which is somewhat flat- 

 tened, a roundish white spot, from which, in consequence of 

 a local multiplication of the blastoderm cells, an area which 

 likewise appears white, but is as yet indistinctly defined, soon 

 extends towards the other pole. Upon this disk-shaped 

 region there now appear, as the earliest traces of the future 

 embryo, a series of transverse furrows, which are at first 

 shallow and which apparently arise almost simultaneously 

 and divide the embryonic rudiment into a number of segments. 

 In the first instance seven such divisions are distinguishable. 

 After the first and largest section — the cephalic plate, which, 

 however, is not yet sharply circumscribed, — the second is 

 constituted by the segment which furnishes the pedipalpi, and 

 this is succeeded posteriorly by four other segments, from 

 which the ambulatory limbs subsequently proceed. Finally 

 the seventh and last section, which, in contradistinction to 

 the other fillet-shaped sections, is semicircular in shape, with 

 its periphery directed forwards, may in consequence of its 

 function be termed the abdominal plate. All these segments 

 are primarily unpaired structures. While, however, they 

 become further and further separated from one another, 

 there soon appears in the median line a shallow and narrow 

 longitudinal groove, which divides the whole of the segments, 

 with the exception of the abdominal plate, into two symme- 

 trical halves. This median furrow proceeds from the poste- 

 rior towards the anterior end of the embryo. The last four 

 thoracic segments are the first to divide, and these are subse- 

 quently followed by the segment which gives rise to the 

 pedipal})i, and thereupon also by the eighth division, the 

 segment of the chelicera3, which has in the meantime become 

 separated off from the cephalic plate, which likewise divides 

 into two apical lobes. While this process is taking place 

 the unpaired abdominal plate increases in breadth ; at its 



