2 bulletin: museum of comparative zoology. 



many of the figures were later redrawn and a number of additional obser- 

 vations made. Practically all of the work upon the metamorphosis of 

 the spermatid was done in the Harvard laboratory. 



It is with pleasiwe that I take this opportunity of expressing my 

 gratitude to Dr. E. L. Mark for much valuable advice and counsel in 

 the work upon Scolopendra, and for his careful reading and criticism of 

 my paper. My thanks are also due to Dr. C. E. McClung for his advice 

 and encouragement during the early part of the work. 



Comparatively little cytological work has ever been done upon the 

 myriapods, probably owing to the difficulty of obtaining material, in the 

 required stages, of the more common members (Geophilus, Julus) of 

 this group. But such difficulties are not experienced in working upon 

 the various species of Lithobius, Scutigera, and Scolopendra. This ap- 

 parent neglect is certainly not due to any lack of excellence in the 

 material, for while the chromosomes are not as large as in the sperm 

 cells of some insects (Acrididae), they are still of such size that their 

 behavior may be followed in the minutest detail, and they are in some 

 respects more favorable than those of other arthropods. Then, too, 

 in the study of other problems than those depending on the size and 

 number of the chromosomes, — such as the behavior of the cytoplasmic 

 structures and the evolution of the spermatid into the spermatozoon, — - 

 the cells of Scolopendra are decidedly superior to those of any other 

 arthropod I have examined. 



The published works upon the spermatogenesis of myriapods may be, 

 divided into two groups : the first comprising the early works by Gilson 

 ('84), Carnoy ('85), and Prenant ('87) ; the second including the later 

 works by P. Bouin (:00, :01, :03), P. et M. Bouin ('99, :02, :03), 

 Bouin et Collin (:Ol), Collin (:Ol), Meves und von Korff (:Ol), and 

 Blackmail (:01, :03). 



The early work of Carnoy ('85) upon the spermatocytes of Lithobius 

 forficatus, Geophilus, Scutigera arachnoides, and Scolopendra dalmatica, 

 while in many respects valuable, contains numerous inaccuracies, as do 

 also the observations of Gilson ('84) and Prenant ('87). These mistakes, 

 which in many cases are doubtless due to the imperfect technique of 

 the time, have at several points been the cause of errors of interpretation. 

 The results of these authors will be discussed later in connection with 

 the observations upon which they have a bearing. 



In 1901 appeared a short paper by Meves und von Korff upon mitosis 

 in Lithobius. Their observations are concerned principally with the 



