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Wisconsin Academy of Scieaces , Arts and Letters. 
emitting at the same time a drop of fluid, which, no doubt, gives a better 
hold. In the parallel case of the Poduridae , M. 1’ Abbe Bourlet supposes 
that the ventral tube act as follows: “1° qu’ il sert a ces insectes a se rnain- 
tenir sur les surfaces perpendiculaires en y faisant le vide; 2° que leliquide 
excrete par lui sert a humecter la queue et la rainure; 3° qu’ il supplee ala 
faiblessedes pattes dans les chutes qui suivent les sauts.” I am, therefore, 
disposed to agree with him in so far as he denies that the adhesive power 
depends altogether on the viscous fluid; but, on the other hand, I cannot 
attach much importance to his two latter suggestions. De Geer well un¬ 
derstood the use of this curious organ. Be says: ‘• Quand la Podure [un¬ 
der which name he includes the present genus Smynthurus ] marchait con- 
tre les parois du poudrier, il lui arrivait souvent de glisser; c’ etait comme 
si les pieds lui manquaient, de fagon qu’ elle etait sur le point de tomber; 
dans F instant meme, les deux filets parurent et furent lances avec rapidite 
hors de leur etui, s’ attachant dans le moment ail verre par la matiere 
gluante dont ils sont enduits, en sorte qu’ alorsla Podure se trouvait comme 
suspendue a ces deux filets.” Nicolet gives a similar explanation of their 
function, and, like De Geer, attributes the adhesiveness to the glutinous 
matter which they secrete.” 
The question has presented itself to me: Is not the collophore developed 
from a pair of true appendages united in the median ventral line, though seri¬ 
ally corresponding with the thoracic legs and hence truly homologous with 
the pleuropodia of insect embryos? Although I have been unable to give 
the subject the careful study which it deserves, I believe that I have un¬ 
earthed a few facts calculated to answer the question in the affirmative. 
The only embryological observations made up to date on the origin of the 
collophore are recorded in Byder's brief account of the development of 
Anurida maritima [’86]. His figures [Figs. (5, 9 and 10, plate 15] show 
clearly that the collophore consists of a pair of true appendages applied to 
each other in the median ventral line, even if he had not expressly stated 
that during the earlier stages the limbs, antennae, collophore, etc., had the 
form of mere blunt, paired papillae, or of blunt, clavate, tentacle-like 
paired outgrowths from the lateral surfaces of the ventral plate or elong¬ 
ated germinal area.” 
I can supplement this embryological evidence by a few observations on 
the collophore of Anurida maritima. This maritime species was found 
in great numbers clinging to the under surfaces of stones between 
tides at Woods Holl, Mass. Its collophore is less complicated than that of 
our common inland forms, and therefore better calculated to give a cor¬ 
rect idea of the fundamental pattern underlying its structure. Specimens 
were killed by being placed for a minute in Carnoy’s fluid heated almost 
to boiling and were then preserved in 80 per cent, alcohol. 
The collophore is quite prominent in surface view (Fig. 16 c.) appearing 
as a heart-shaped tubercle on the middle of the ventral face of the basal 
abdominal segment. The lateral edges are raised to form distinct rims, 
