STOLON FORMATION IN SPECIES OP TRYPANOSYLLIS. 433 
of vacuolated cells. From their position I think there is no 
doubt that they are nephridia, but it is exceedingly diflScult 
to make out their internal opening. They occur both in T. 
gemniipara and T. crosslandi. 
These bodies are figured and described by Johnson, but he 
chooses to regard them as parapodial glands, identical with 
those structures in other Syllids. 1 think that he is without 
doubt wrong, for the parapodial glands are not hollow 
structures such as we find here. He says, moreover, that 
the glands are not only relatively but ’ absolutely larger 
in the caudal segments (i. e. in the genital appendage) and 
in the buds than in the stock,^’ and this fact, which is con- 
firmed in my material, points to a direct connection with the 
occurrence of the sexual products in these parts. We know 
that the nephridia function as generative ducts in Syllids and 
increase in size at reproductive maturity, but there is no 
reason for regarding the parapodial glands, whose oflfice is 
the seci’etion of mucus, as in any way correlated with the 
generative organs. 
In T. crosslandi (3) only a few mature female stolons 
remained attached to the stock, and one of these which was 
cut in transverse section showed the whole of the coelom to 
be crammed with large-sized eggs. The body-wall was 
reduced to a thin skin, the parapodial muscles and the setae 
but slightly developed, and the notopodium hardly perceptible. 
The stolon was, in fact, reduced to a bag of eggs, and it is 
difficult to imagine the mature female bud as capable of 
locomotion. 
A word or two may be added to emphasise the late forma- 
tion of -the head. It is probably the last segment to be 
established. The brain, it is stated by Johnson, develops 
independently of the nerve-cord by the modification of a 
mass of ectoderm cells, and he states that the eyes are inner- 
vated, not fr'om the brain, but from the nerve-cord. Un- 
doubtedly the brain is only differentiated when the full 
number of segments have been formed in the stolon, and the 
otlier head stnictures, such as eyes, are being developed. 
