A STUDY OF METAMERISM. 



395 



A Study of Metamerism. 



By 



T. H. Morgan, Ph.D., 



Associate Professor of Biology, Bryn Mawr College, U.S.A. 



With Plates 40-43. 



Table of Contents. 



I. Typical Forms of ModiQcation in Annelids 

 II, Variation in the Position of the Reproductive Organs 



III. Abnormalities in Front of or including the 15th Metamere 



IV. Study of Embryos 



V. Abnormalities at the Posterior End . 



VI. Modification of Internal Structures . 

 VII. Study of Polychsetous Annelids and Leeches 



VIII. Summary 



IX. Modifications in Antennae of Arthropods . 

 X. Abnormal Metamerism of Locust 

 XI. Study of Colour-bands of Echinoderms . 

 XII. Regeneration in Earthworms . 

 XIII. General Conclusions 



PAGE 



395 

 403 

 407 

 418 

 421 

 425 

 428 

 431 

 435 

 437 

 439 

 445 

 460 



I. Typical Forms of Modification. 



That there were occasionally to be found in the Annelids 

 irregularities in the serial repetition of the rings seems to have 

 been known to several of the earlier writers on descriptive and 

 systematic zoology. The fact did not attract more than a 

 passing attention, and such irregularities were relegated to 

 that waste- heap of abnormalities from which subsequent in- 

 vestigation has often drawn valuable material. 



Simultaneously in 1892 two articles appeared dealing with 



