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 Montagna belong to the family of the Aeolidiidae; 
AmphiporuSy Tetrastemma , Zygonemertes , and Stichostemma are 
Metanemertini; and Linens and Cerebratulus are Heteronemer- 
tini; Polydora is a Polychaete; and Piscicola a rhynchobdellid 
leech. 
The present paper was sent to Dr. Whitman, editor of 
the Journal of Morphology , 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 
