558 DR. R. VON LENDENFELD ON THE SYSTEMATIC [ Dec. 21, 
other leg of the cock grew as usual. This experiment I have 
repeated several times in the same manner, with the same effects, 
which led me to conceive that the spur of a cock would not grow 
upon a hen, and that they were, therefore, to be considered as distinet 
animals, having very distinct powers. In order to ascertain this, I 
took the spurs of hen chickens and placed them on the legs of young 
cocks. I found that those which took root grew nearly as fast, and 
to as large a size as the natural spur on the other leg, which 
appeared to be a contradiction to my other experiments. Upon 
another examination of my hens, however, I found that the spurs had 
grown considerably, although they had taken several years to do it ; 
for I found that the same quantity of growth in the spur of a cock, 
while on the cock, during one year, was as much as that of the cock’s 
spur on the hen in the course of three or four years, or as three 
or four to one; whereas the growth of the hen’s spur on the cock 
was to that of the proper spur of the hen as two to one.” 
When a female animal belonging to a dimorphic species assumes 
male characters, it is truly an example of Atavism, or development 
of transmitted characters normally latent. 
This part of the matter has been dwelt upon at some length for 
the following important reason. If we regard the epiblast and 
the structures developed therefrom as representing the chief cha- 
racters derived from the male parent, it opens up a field of interesting 
inquiry in clinical medicine and pathology regarding hereditary 
diseases, and it demonstrates clearly enough that we have little 
knowledge concerning the germs of organs which may be latent in 
an animal; therefore Neogenetic Atavism is, at its best, exceedingly 
questionable. To assume that such a form of Atavism exists, is to 
believe in the sudden development of new characters: this is totally 
opposed to the fundamental principles of Evolution. 
The question is one of great importance to the pathologist, 
inasmuch as there is very great probability that many aberrations of 
organs and tissues are atavistic in their nature. 
2. On the Systematic Position and Classification of Sponges. 
By R. v. Lenpenrerp, Ph.D., F.L.S., Assistant in the 
Biological Laboratory of University College, London. 
[Received December 20, 1886.] 
I. Introductory Remarks, p. 558. 
IL. Nomenclature of Spicules, p. 559. 
III. The Systematic Position of Sponges, p. 564. 
IV. The Classification of Sponges, p. 570. 
V. Key to the Recent Families of Sponges, p. 589. 
VI. Appendix. List of Publications, p. 592. 
I. InrRopuctrory Remarks. 
Our knowledge of the development and structure of Sponges is of 
such recent date that we have hardly had time to utilize it for 
systematic purposes till now. 
