534, FRANK E. BEDDARD. 
and Lumbricus Dr. Bergh is very possibly right, but I 
must object to his curt dismissal of the arguments to be 
derived from the “ network ” of Perichzta with the remark, 
“Gewisse anatomische Verhialtnisse (Existenz eines ‘ nephri- 
dialen Netzwerkes’ bei Perichzta und bei einigen anderen 
hochdifferenzirten Regenwiirmern), die ohne Weiteres, als 
*urspringlich Einrichtungen gedeutet werden.” In the first 
place, “ einigen ” ought to be replaced by “ vielen ;” and in the 
second place, to state that Perichzta and those other forms 
in which the “plectonephric ” condition occurs are highly 
differentiated is, at least, begging the question. Finally, 
neither Spencer nor I assumed the primitive character of the 
nephridia in these types “ ohne Weiteres.” 
At the same time I freely admit that the observations 
recorded in the present paper, added to those of Bergh, Kleinen- 
berg, and Wilson, have shaken considerably the position 
which I have taken up in regard to the phylogenetic develop- 
ment of the nephridia in the Oligocheta. 
They seem to show that paired nephridia in this group are 
earlier than the irregular network. It must be remembered, 
however, that the permanent nephridia of Lumbricus cannot 
be the precise equivalents of the nephridia of the embryo Acan- 
thodrilus; the reason for this is that the permanent nephridia 
of Lumbricus are developed out of the pronephridia. It is 
true that in Lumbricus there appears to be no break in 
continuity ; the pronephridia are converted into nephridia by 
a gradual series of changes. In Rhynchelmis, however, the 
pronephridial stage is marked by the single “ flame-cell ” 
which afterwards, by division, develops into the funnel. In 
Acanthodrilus there is a break between the pronephridia 
and the permanent nephridia; this is marked not only by the 
disappearance of the funnels, but also by the occlusion of the 
lumen of the tubules. This would seem to imply a temporary 
cessation of function or at least an alteration of function 
in the nephridia. 
It is interesting to notice that the enormous development of 
perivisceral corpuscles loaded with secreted granules occurs 
