No. 2.] COMPARATIVE CYTOLOGICAL STUDIES. 267 



of Berlin ; and the preparations of the siphonophore Rodalia 

 were kindly placed at my disposal by Dr. E. G. Conklin. 



Doto and Alontagua belong to the family of the Atolidiidae ; 

 Anipliiporus, Tetrastemma, Zygonemertes, and Stichostemma are 

 Metaneniertini ; and Linens and Cerebratultts are Heterotiemer- 

 tini; Polydora is a Polychacte ; and Piscicola a rhynchobdellid 

 leech. 



The present paper was sent to Dr. Whitman, editor of 

 the Journal of Morpliology, on Feb. 3, 1897 ; on receiving the 

 MSS. again in March, 1898, I was able to incorporate in the 

 text reviews of the literature of the whole year 1897. No 

 other changes of importance, however, were then made in the 

 original text, except brief mention of observations which I had 

 made in the past year. It is my intention to follow this paper 

 by others on nucleolar structures, particularly on structures 

 which have received but little consideration in the present 

 paper, namely, "double" nucleoli and chromatin nucleoli. 



II. REVIEW OF THE LITERATURE UPON NUCLEOLI. 



In this review shall be considered separately, first, those 

 papers from the zoological, and, second, those from the 

 botanical standpoint. The references from zoological papers 

 I have endeavored to make as complete as possible, while my 

 citations from the observations of botanical observers are 

 much less numerous, though even in this I have consulted the 

 more important papers from 1880 to the present time. In 

 referring to the zoological papers, I have taken them up in 

 chronological order ; and in doing so, shall treat separately 

 the periods 1781-1860, 1861-69, 1870-79, and from the year 

 1880 to the present time I shall treat the literature for each 

 year separately, in order that the reader may more conven- 

 iently be able to turn to the citations from a given paper. 

 Under each year papers are reviewed according to the alpha- 

 betical sequence of the authors' names. The botanical 

 literature, on the other hand, shall simply be treated in 

 chronological order, without regard to any division into periods. 

 The full titles of the papers referred to are to be found on 



