290 Mr. F. E. Beddard on the possible Origin 
gical period from the Upper Silurian strata to the Miocene 
inclusively. 
Whether this non-existence of the Horny Sponges must be 
left for further investigation to verify or whether it can be 
explained by deferred development, that is to the present era, 
or in any other way, I will not go further here than the fact 
that the Horny Sponges are by far the most abundant at the 
present day and yet have no fossil representative. 
XXXVIII.—On the possible Origin of the Malpighian Tubules 
in the Arthropoda. By Frank KE. Bepparp, M.A., 
F.Z.8. 
THERE are two sets of structures in the Arthropoda which 
have been proved to possess a renal function and which have 
been regarded as possibly equivalent to the nephridia of 
worms. 
The “green glands” of the Crustacea are commonly 
regarded as nephridia, and researches now in progress will, I 
believe, establish the nephridial nature of these organs upon 
a very firm basis of fact. 
Among the Arthropoda another class of renal organs exists 
in the’ so-called Malpighian ceca. These occur in a few 
Crustacea, e. g. the Amphipoda (Spencer, “ The Urinary 
Organs of the Amphipoda,” Quart. Journ. Micr. Sci. xxv. 
1885), and in Tracheata; in the latter group they consist of 
a variable number of glandular ceca which grow out from 
the proctodeum ; in the Amphipoda, on the contrary, Spen- 
cer finds reasons for believing that the tubes in question are 
diverticula of the mesenteron. 
The only known Arthropod with unmistakable nephridia, 
paired and metamerically arranged, is Pertpatus. ‘The exist- 
ence of these organs was originally pointed out by Balfour 
(“On some Points in the Anatomy of Peripatus capensis,” 
Quart. Journ. Micr. Sci. xx. 1880), and has been since care- 
fully studied from the developmental as well as from the 
structural point of view by Sedgwick (“A Monograph of the 
Development of Peripatus capensis,” Stud. Morph. Lab. Cam- 
bridge, vol. iv. pt. 1.). Lankester had previously pointed out 
that the ‘ coxal glands” of Limulus were in all probability 
to be regarded as modified nephridia, and this position is 
strongly supported by Sedgwick’s results. So far as our 
present knowledge goes it may be safely assumed that the 
