Fbbruaey 2, 1900.] 



SCIENCE. 



175 



attain the value of a distinct individual, as 

 compared with the fission in other annelids 

 {Dero, Aeolosoma) , but the entire process is 

 more like the sexual fragmentation described 

 for the Palolo worm. 



Metamerism of the Leech. W. E. Castle. 



Following Gratiolet, most students of 

 leech metamerism regard the annulus which 

 bears the metameric sense organs as the 

 first (most anterior) annulus of the somite. 

 Careful study shows, however, that the 

 sensory annulus is really the middle, not 

 the most anterior ring of the somite. 



The true limits of the somite are indicated 

 by the distribution of the metameric nerves, 

 all the annuli of a somite being innervated 

 from one and the same ganglion. This is 

 shown by the following facts : 



1. In somite abbreviation rings inner- 

 vated from the same ganglion fuse together. 



2. In somite growth (multiplication of 

 annuli) new rings appear chiefly at the 

 limits of the somite (as defined), usually 

 first at the posterior, then at the anterior 

 end of the somite. 



3. An abnormal animal, in which a 

 somite is wanting in either half of the body, 

 shows tliat the missing rings form a somite, 

 limited as stated above. 



The multi-annulate structure of the leech 

 somite is correlated with the restricted 

 number of somites in the body (thirty-four 

 both in the Rhyncobdellidai and in the 

 Gnathohdellidse). Increase in length of 

 body and complexity of structure has been 

 brought about not by multiplication of 

 somites, as in the Chsetopoda, but by 

 elongation of existing somites and multipli- 

 cation of their annuli. 



Whitman and Bristol have established 

 the derivation of the five-ringed type of 

 somite from the three-ringed type; several 

 facta indicated the probable earlier deriva- 

 tion of both from a one-ringed type of 

 somite. Among these may be mentioned 



the manner of somite abbreviation and the 

 structure of the somite in Branchiobdella 

 and related forms. 



The development of the pigment and color 

 pattern in Coleoptera: W. L. Towee. 

 The object of this research was to find 

 out if possible: (I.) the way in which the 

 colored patterns developed, and the se- 

 quence of the colors in ontogeny, (II.) the 

 origin of the pigment and its development^ 

 (III.) something of its composition. 



I. In Coleoptera two types of colorations 

 are found. 



(1) Unicolorous, where the whole animal 

 is of one color. 



(2) Multicolorous, where there is a color 

 pattern of two or more colors. 



I have studied the development of the 

 color pattern in several forms of each type. 



After the larva transforms to a pupa it 

 is white or pale yellow. Color first appears 

 on the cuticula of the future beetle about 

 the opening of the spiracles, i. e., where the 

 spiracular muscles are attached to the cu- 

 ticula. Color next appears upon the pro- 

 thorax as two bands laterad of the median 

 line, then a more or less broken band laterad 

 of the first two appears, and last of all two 

 spots at the anterior and posterior outer 

 angles. The places where color first ap- 

 pears is over the attachment of the muscles 

 to the cuticula. These spots may all be- 

 come united as in the unicolorous, or re- 

 main separated as in multicolorous type 

 forms. Color next appears upon the head, 

 over the attachment of the cranial muscles 

 to the cuticula, and then color appears upon 

 the ventral abdominal surface over the mus- 

 cular attachments. 



The color as it first appears is pale yel- 

 lowish brown which rapidly darkens, be- 

 comes very dark brown or black. This 

 dark or black color is, according to Hagen, 

 dermal pigment: There are some beetles 

 that have a unicolorous type of color 



