ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 529 



of mutual toleration such as exists in social communities. In this case, 

 however, if adults of both sexes are confined closely together, they will, 

 regardless of sex, fall upon each other, amputating antennae and legs 

 with a savagery like that of the most bloodthirsty quadruped. 



S. Arachnida. 



Grasping Organs in Pediculidae.* — H. Osborn describes in Hcema- 

 topinus urius, H. macrocephalus, and Euhmnatopinus ahiormis, pro- 

 tractile discs upon the legs, whose function appears to be that of holding 

 on to the hair. The disc, which in H. urius is at the distal end of the 

 tibia, plays back and forth in a pit-like depression. There is a large 

 muscle running through the tibia and forking near the middle of the 

 tibial joint, one part going to the tibial spur, the other passing on to the 

 tarsal joint, while from the latter a fibre runs to the base of the pro- 

 tractile disc. Muscular elements for protraction are apparently absent, 

 and this may be provided for in the movements of the chitinous wall, 

 assisted partially by the flexion of the tarsal joint. 



Pycnogonida of West Coast of North America.f — Leon J. Cole 

 gives an account of the Pycnogonida collected by the Harriman Alaska 

 Expedition. The collection includes thirteen species, representing nine- 

 teen genera. After notes on the geographical distribution, the author 

 discusses the classification and terminology, giving a useful tabular 

 summary of the names used by various recent investigators. He also 

 gives a diagnostic key to the species described in his memoir, which is 

 admirablv illustrated. 



e. Crustacea. 



Maturation Divisions in Testicle of a Lobster.! — A. Labbe 

 observes that in the state of synapsis the chromosomes unite two and 

 two, and fuse their chromatin into a single or protetrad body. The 

 tetrads arise from the protetrads by quaternary condensation of the 

 chromatin. In the constitution there is no question of longitudinal or 

 transverse division. Before the formation of the protetrads the thread 

 prepared for the first maturation division undergoes a first longitudinal 

 division, which effaces itself. At the first metaphase there is a second 

 division (? longitudinal) which appears preparatory to the second 

 kinesis and does not efface itself, but is useless, since it separates two 

 demi-dyads which will pass into the same spermatid. These two 

 divisions are quite independent of the formation of tetrads. They seem 

 only a suggestion of ordinary mitoses, and are objectless. The mode of 

 formation of the quaternary groups shows that the chromatin mass of 

 a protetrad separates into four, without involving either equational or 

 reduction division. The author is inclined to deduce from these facts 

 qualitative differences between the conjugated chromosomes as important 

 as exist between ovum and spermatozoon. 



* Ohio Naturalist, iv. (1904) pp. 107-8. 



t Harrimau Alaska Exped., x. (1904) pp. 249-98 (18 pis.). 



\ Comptes Rendus, cxxxviii. (1904) pp. 9G-9. 



