CORRESPONDENCE. 



Reply to Criticism upon " Notes from the Geological Laboratory " of the 



Johns Hopkins University. 



The criticisms contained in your last number (p. 4) upon the methods of specific 

 description employed in the " Notes from the Geological Laboratory," arise from an 

 entirely erroneous conception of the character of the articles presented. These 

 articles were intended simply as reviews of investigations carried on during the past 

 year at the geological laboratory, and were not intended to give more than an out- 

 line of results. The full reports, and, to a large extent the plates also, have been 

 already prepared for final publication and will shortly appear from the press. No pre- 

 tence was made to give full diagnoses of the forms described, while it was distinctly 

 stated that " The species referred to in the accompanying list have been largely 

 figured, and the plates, together with the fuller descriptions of the forms, will be 

 found in the forthcoming Government report." 



Your stricture regarding the multiplication of new species, which is applicable 

 to work in areas where a sufficient number of characteristic forms has been already 

 described, does not fit a case like that of the Eocene of the Middle Atlantic slope, 

 where the fauna is practically unknown, and where the amount of information has 

 been wholly insufficient for stratigraphical purposes. The synonymy of the few 

 species described by previous writers from this area has not been ignored, as an 

 examination of the review will show. 



The Circulars of the Johns Hopkins University have long afforded the scientific 

 departments the means of bringing forward, in the form of preliminary notices and 

 reviews, the investigations which are being conducted in the laboratories and have 

 never been regarded as a permanent medium of publication. 



Johns Hopkins University. William B. Clark. 



[We welcome Professor Clark's letter, as it affords additional argument in 

 support of our remarks on "The Preliminary Notice " (see antea.p. 73). — Editor, 

 Nat. Sci.] . 



Reducing Divisions in the Formation of the Polar Bodies. — A Correction. 



The review of my "Atlas of Fertilisation," pubhshed in Natural Science for 

 December, 1895, contains a misinterpretatipn of my views regarding the phenomena 

 of maturation that I trust you will allow me to correct. The passage reads : — 



"It is clear that the distinction between reducing divisions and ordinary 

 divisions suggested by Professor Weismann cannot be applied to the formation of 

 the polar bodies as interpreted by Professor Wilson " (p. 37S). 



There is nothing, I think, in the brief account of maturation given at pp. 9, 10 

 of the Atlas, or in the accompanying figures, to bear out this statement. The 

 ultimate problem of reduction, as Boveri long since pointed out, lies in the mode of 

 origin of the tetrads, of which nothing is said in the Atlas, since my purpose was only 

 to give an outline of the broader features of maturation. The work of Hacker and 

 Riickert seems to leave no doubt that in the copepods the origin of the tetrads is 

 such that the division of the dyads during the formation of the second polar body 

 must be interpreted as a " reducing division " in accordance with Weismann's 

 earlier views. This result is diametrically opposed to the conclusions of Boveri, 

 Hertwig, and Brauer in the case of Ascaris, and cannot at present be reconciled with 

 them. It was on account of this contradiction that the origin of the tetrads was 

 not critically considered in the Atlas. The account there given, which considers 



