ZOOLOGY AND BOTANY, MICROSCOPY, ETC. 
531 
front of, or at least in a line with, the jaw-pieces of the second pair of 
appendages is a very primitive feature retained by Triartlirus ; while in 
Apus, and still more in Limulus, there is much greater specialization ; 
in fact, we can trace through these three genera the greater modification 
of the labium from its primitive condition as a ridge-like posterior 
border of the mouth, such as the “ bent annelid ” theory demands, into 
the pair of specialized and enigmatical lobes found in Limulus. The 
original similarity of the limbs of the head and of the trunk, which the 
annelidan theory demands, is still found in Triarthrus. In fact, Triartlirus 
represents the primitive type of mouth-formula. A study of the appen- 
dages of the trunk shows that the Trilobites, as exemplified by Triarthrus , 
in spite of their extremely primitive mouth-formula, do not stand in the 
direct line of descent of the Crustacea, but are lateral offshoots, specialised 
for a creeping manner of life. Mr. Bernard urges that the discovery of 
tufts of setae on the limbs of Triarthrus at practically the very spot 
where, in Apus, he assumed their former presence, may be fairly claimed 
as one more slight confirmation of his general argument. Summing up 
the new and important facts described by Dr. Beecher with the known 
conditions of Apus, we find that the Crustacea can now be linked, step 
by step, with the Chaetopod Annelids, while the line of development is 
practically that which the author sketched in his former paper.* We 
are now in a position to supplement that scheme by additional details 
which bring it still closer to the actual order. These points the author 
briefly indicates. 
Annulata. 
Tube-forming Habits of Panthalis oerstedi.f — Mr. A. T. Watson 
gives an interesting account of his observations on the formation of these 
tubes. They were first observed in dredging off the Isle of Man. A 
number of long, curious, soft muddy masses were brought to the surface, 
and as nothing was known about them they were described as “ mud- 
sausages.” Many of those that are dredged are empty, but others are 
inhabited and the most frequent tenant is a Panthalis. The question to 
decide first of all was whether the Panthalis was the fabricator of the 
tubes or simply a tenant. The genus in question is one of the Acoetidse, 
all the members of which are rare. The author describes how, in the 
laboratory at Port Erin, he made observations on this worm and was able 
to see how the tube was made. The mucus-like threads which form the 
bases of the tubes are derived from glands which exist in all the parapodia 
of the worm except the anterior eight pairs. 
Javan Perichaetidae.t — Dr. W. B. Benham gives an account of three 
species from Java which are nearly allied to one another and to others 
previously recorded from the same island. It appears that Dr. Benham 
is inclined to lay considerable stress on the colour and dimensions of the 
worms in question, for in our endemic forms these characters are very 
constant. We have yet to learn how far the size of the prostate and of 
the diverticula of the spermathecie are liable to variation, either in 
relation to functional activity or to other circumstances. 
* See this Journal, 1894, p. 562. 
t Trans. Liverpool Biol. Soc., ix. (1895) pp. 169-88 (2 pis.). 
t Ann. and Mag. Nat. Hist., xvi. (1895) pp. 40-51 (1 pi.). 
