THE DEVELOPMENT OF ADMETUS PUMILIO. 625 



fectly round, aud stains very deeply with lisematoxyliu. It 

 is almost always surrounded by a clear space containing 

 little stainable matter. It is always found inside tlie 

 nucleus. 



The average measurements of the genital cells are : — 

 Length of cell "07 mm,, breadth of cell "03 mm., length of 

 nucleus '03 mm., breadth of nucleus '02 mm., diameter of 

 micro-nucleus '004 mm. 



11. The Muscles. — The two chief systems of muscles 

 have already been referred to under the heading Coelom. 

 They are at this stage very well developed, and are composed 

 of smooth fibres only. 



Pereyaslawzewa (38) declares that the muscles of the 

 cephalothorax are all striated, those of the abdomen being 

 all smooth. It is hard to understand why this should be 

 the case, and I think that the statement requires further 

 confirmation, especially as all the muscles are derived from 

 the same segmental sources, both in cephalothorax and 

 abdomen. 



12. The Yolk. — It is now only necessary to state that 

 pari passu with the development of the central nervous 

 system, and with the contraction and withdrawal of the 

 ventral ganglion-cord into the cephalothorax, the chief bulk 

 of the yolk has been forced back into the abdomen, as is 

 the case with all Arachnids. 



Conclusions. 



On the Avhole the development of the Pedipalps follows 

 the types prevalent among other Arachnids, sometimes 

 leaning more towards the one, sometimes more towards the 

 other class. It resembles — 

 (1) That of Spiders : 



a. In the first cleavages (probably). 

 h. In the egg-envelopes. 



c. In the general build of the blastoderm. 



d. In the development outside the mother animal. 



