482 Dr. Fritz Miiller on the 
Alexander Agassiz has since expressed himself similarly ; 
and I also find the same doubts repeated by Dr. Paul Meyer * 
in a criticism of Claus’s latest work (‘ Investigations for the 
Discovery of the Genealogical Foundation of the Crustaceous 
System ’). 
The development of Nauplius-like larvee into Macrurous 
Crustacea is of such importance to the genealogy of the 
Crustacea that it does not seem superfluous to point out once 
more the reasons which induce me even now to look upon the 
course of development described by me as a completely assured 
fact. I repeat, for this reason, literally, what I wrote in Oc- 
tober 1864 as a reply to Spence Bate’s doubts. 
The requirement that one should only ascribe early forms 
to definite parents when one has obtained them from the ova 
taken from the parent, seems to me to be unreasonable. 
If one admitted that, it would naturally be demanded not 
only for the earliest forms, but, with equal justice, for all 
young (intermediate) forms. It would be necessary to 
demand for every stage either that it be reared from the ovum 
or preserved alive until it arrives at sexual maturity; and 
this condition would compel us to give up the study of the 
development of most marine animals. I contend that it 
is quite enough that we should be able to unite the terminal 
members of the series by a continuous chain of intervening 
forms so closely united that there cannot be any reasonable 
doubt about the connexion of any two successive forms. But 
the proof of the connexion of my Nauplius with the Peneus, 
or a genus nearly related to it, I believe to have been esta- 
blished in a sufficient manner. 
In a journal which has only twelve plates in a year I could 
not, as Spence Bate has done for his memoir on the develop- 
ment of Carcinus menas, obtain seven plates for one essay. 
I had therefore to limit myself to illustrating only a few of the 
most interesting forms out of fifty pages of drawings of the 
development of the prawns produced from the Nauplius stage. 
At the same time it appeared to me unnecessary to remark 
that the metamorphosis of one form into the other had not 
been imagined, but was the result of close observation of 
numerous larvee. 
Only in one place there were not at my command interve- 
ning forms in abundance. 
Between the Nauplius (pl. ii. fig. 2) and ithe Zoéa repre- 
sented in fig. 4 I had only one opportunity of observing (in 
the same species) two intervening forms, which I mentioned— 
* Jenaer Literaturzeitung, 1877, No, 16, p. 247. 
