March 10, 1905.] 



SCIENCE. 



385 



spondenee of marginal plates with sutures 

 between scutes is retained in several shells 

 abnormal in the marginal region. In the 

 costal series the seventh forms an excep- 

 tion : but it harmonizes with the others fall- 

 ing into the alternating series, and bearing 

 the triradiate impression of scute sutures in 

 several specimens that have a supernum- 

 erary neural in the posterior region. In 

 shells abnormal as regards scutes, the nor- 

 mal condition of correlation may tend to 

 be preserved by associated (correlated) ab- 

 normalities in bony plates. 



The presence, in correlation with super- 

 numerary scutes, of a ninth costal plate 

 may be an atavism. In such cases observed, 

 the tenth rib, instead of as normally anchy- 

 losing with the ninth rib and eighth costal 

 plate, enters into the ninth costal plate ; so 

 that each dorsal rib, except the first, forms 

 part of a plate. 



More complete results, with drawings 

 and photographs, are in preparation for 

 publication. 



On the Nature and Behavior of the Mor- 

 phogenoiis Siihsiances in the Egg of 

 Chcetopterus: Frank R". Lillie, Uni- 

 versity of Chicago. 



Eggs of Chmtopterus may be stimulated 

 to undergo differentiation of certain kinds 

 without the process of cleavage by a 

 variety of methods. Such unsegmented 

 ova develop cilia and swim about actively. 

 The protoplasm is vacuolated like that of 

 the normal larvaj and the yolk is aggre- 

 gated in a manner resembling that in the 

 normal development. 



Careful examination of this mode of 

 development, however produced, showed 

 that it proceeds by the segregation and 

 differentiation of substances readily dis- 

 tinguished by their optical properties and 

 by their behavior. The sequence of events 

 is somewhat obscured and complicated by 

 amoeboid movements of the protoplasm, but 



is essentially the same in all ova. Five 

 separate substances may be readily distin- 

 guished, arranged like a series of strata, 

 prior to the appearance of the cilia ; one 

 of these overflows the remainder and cilia 

 develop from this layer alone, which is 

 characterized by the presence of ijeculiar 

 granules. 



The same substances may be recognized 

 in the normal unsegmented egg where they 

 have a different arrangement, and they 

 may be followed in the normal develop- 

 ment. They thus appear to be specific in 

 their morphogenic properties, both in the 

 normal and in the modified development. 

 j\Iorphologically these substances are distin- 

 guishable only by differences in the size, 

 arrangement and microchemical reactions 

 of the larger spherules, and not at all by 

 local differentiation of the microsomes or 

 ground substance of the protoplasm. The 

 conclusion appears inevitable that in 

 Chmtopterus at least, the differences be- 

 tween specific morphogenic substances are 

 dependent, certainly in part, on the nature 

 of the spherules contained. 



The observations led to the conclusion 

 that these spherules exhibit attractions and 

 repulsions among themselves, which may, 

 to a great extent, explain their segregation 

 and arrangement. 



The spherules have all been lumped to- 

 gether as 'yolk' in the egg of Chmtopterus. 

 In other animals, also, is the so-called yolk 

 really a mixture of various substances? 

 It is in any event certain that we have no 

 precise criterion of yolk in holoblastic eggs, 

 and one is badly needed. 



The Structure of Bothriolepis. with Exhibi- 

 tion of Specimens of Devonian Fishes of 

 Canada: "William Patten, Dartmouth 

 College. 



This paper was based on a large collec- 

 tion of new material recently acquired by 

 the author from New Brunswick. Numer- 



