452 E. ELEANOR CAROTHERS 



I wish to thank Dr. McClung for many helpful suggestions and 

 much kindly interest as well as for material from his own col- 

 lection. It is also through his efforts that I am indebted to the 

 University of Pennsylvania for a collecting trip during the sum- 

 mer of 1915 to obtain additional material. I am, besides, in- 

 debted to the Marine Biological Station at Woods Hole for 

 laboratory facilities during the summer of 1914. I also wish to 

 express my thanks to Mr. J. A. G. Rehn and Mr. Morgan Hebard 

 of the Academy of Natural Science for the identification of the 

 specimens and helpful suggestions concerning the taxonomy of 

 the group, and finally to Dr. D. H. Wenrich for much kindly 

 cooperation. 



11. OBSERVATIONS 



Since the evidence for segregation and recombination must be 

 derived largely from the maturation divisions, I shall begin with 

 the first spermatocytes, then go back to the spermatogonia and 

 to the somatic complexes of the female for corroborative evi- 

 dence, and finally, take up the second spermatocytes, which are 

 morphologically related directly to the spermatogonia! and so- 

 matic complexes. The individuals are numbered consecutively. 

 Where more than one complex is shown from an individual the 

 succeeding ones are indicated by letters; e.g., number 1 always 

 refers to a given animal; the letters after the 1 (atox) designate 

 drawings from this specimen. 



1 . First spermatocytes 



a. Segregation of homologues of J -shaped tetrads in individual 

 no. 1, Trimerotropis (?) suffusa (?). This is one of two indi- 

 viduals belonging to what I designate as form 'B.' They were 

 collected on Orcas Island in Puget Sound by a party from 

 Kansas University in the summer of 1909. Both individuals are 

 alike. 



Of the twelve first spermatocyte chromosomes (plate 1), four 

 (nos. 9 to 12) are atelomitic — Stenobothrus type (McClung, 

 '14) — four (nos. 2, 3, 5, and 6) are telomitic — Hippiscus type, 

 the accessory (no. 4) is V-shaped, atelomitic, while the remain- 

 ing three tetrads (nos. 1, 7 and 8) have one dyad of the Steno- 

 bothrus type and the other of the Hippiscus type. 



