THE DEVELOPMEiNT OP ADMBTUS PUMILIO 005 



conimmiicates with the yolk of the embryo. Later on this 

 opening closes, after which the lateral organ becomes func- 

 tionless and drops off. 



The lateral organ of the Thelyphonidas has been 

 described by Strubell (41), and there is no doubt that it is 

 identical with that of Admetus. In other orders of 

 Arachnids we only find the lateral organ in Solpugids and 

 Pseudo-scorpions. 



Croneberg (10) described the lateral organ of Galeodes. 

 This also seems to be very similar to that of Admetus. I 

 have also been able to find a similar oi'gan in a young adult 

 Chelifer; it seems to me to have already become functionless, 

 and much resembles that described for Admetus in the fifth 

 stage. The possession of a lateral organ seems to me to 

 point out a nearer relationship between these three groups. 



(4) The Coxal Gland. — There is in Admetus, as in 

 all Arachnids, a so-called coxal gland. I have found it, 

 like the authors already cited^ Miss Pereyaslawzewa ex- 

 cepted, at the base of the third extremity; I am also 

 able to prove its existence, if only as a rudiment, at the 

 base of the fourth extremity. This last atrophies very 

 soon. At this stage the coxal gland consists of a per- 

 fectly straight tube, running from the under surface of the 

 coxa inwards, and lying immediately on the surface of the 

 brain itself. It is easily distinguishable from the brain by the 

 lighter tinction of its nuclei. It is everywhere surrounded by 

 connective tissue. Whether it is still in open communication 

 with the coelom or no I am not able to decide. The occur- 

 rence of the coxal gland at this stage in the fourth extremity as 

 well as the tliird makes it appear probable that it was origi- 

 nally segmental, as in scorpions, and it is likely that it would 

 be discoverable in every segment in earlier stages of 

 growth. 



(5) The Nervous System and Sense-organs. — 

 The nervous system at this stage consists of the cerebral 

 ganglia and of the ventral ganglion-cord ; this last extends 

 far into the abdomen. 



VOL. 45, PART 4. — NEW SERIES. fi S 



