DINOPHILUS, POLYGOKDIUS, EOHIUKUS, AND PHORONIS. 115 
is to Shearer (13) that we owe the first clear and definite 
account of the development of the solenocytes themselves. 
They arise from the wall of the ectodermal pit, as is con- 
vincingly shown in his figui’es. 
During a visit to Helgoland last year I was able again to 
study the nephridium in a living Actinotrocha larva (A. 
branchiata). In this form it is a large organ with abi’anched 
internal end lying in the preseptal haemocoele. As shown in 
fig. 4, multitudes of solenocytes project from the wall of the 
nephridial canal. The nuclei are placed, not at the extreme 
end of each tube, but rather at the side. Now it is well known 
that an accumulation of blood-corpuscles is generally found 
in the immediate neighbourhood of the nephx’idium in these 
larvse, and the interesting new point I have to bring forward 
is this — that very long, stiff cilia are set among the soleno- 
cytes, attached by their base to the wall of the nephridium 
between the solenocyte tubes. 
Although I did not observe these cilia move very actively 
in the larva compressed under a cover-slip, yet I have little 
doubt that the}”^ agitate the blood-fluid, and so lead to the 
gathering of the corpuscles just mentioned. I have described 
almost exactly similar cilia on the nephridia of the Alciopids 
(2), but in these Polychaetes they lie, of course, in the coelom. 
Actinotrocha is the only form, so far as I know, in which 
they occur on a nephridium projecting into a haemocoelic 
space. 
The Larva of Polygordius. 
Since the figure of the nephridium of a larva from Ceylon 
published in 1900 (2) w'as based on somewhat doubtful observa- 
tions made on scanty material, I have here given a new and 
more complete representation of the whole organ (fig. 2) as it 
occurs in the Neapolitan species. The drawing was carefully 
made from the living larvae of about the stage shown in fig. 
8, PI. 11, of Fraipont’s well-known monograph (4). It will 
be seen at once that the new figure confirms in every I’espect 
the account I previously gave, in which it was first shown 
