SIR JOHN LUBBOCK ON THYSANURA. 283 
The smaller are three-jointed, much expanded at the apex. The lower lip is four- 
lobed; but the lobes are rounded, not pointed as in Treviranus's figure *. 
The legs are five-jointed, and the feet biunguiculate. The two basal segments bear a 
number of stiff spines with bifurcate extremities, like those on the larger palpi (in addi- 
tion to ordinary hairs). On the underside of each thoracic segment is a sort of flap, 
beautifully covered with scales. That of the prothorax is very large; the other two are 
smaller, particularly the one belonging to the metathorax. 
The abdominal appendages are confined to the two posterior segments. They are 
represented, however, on the anterior ones by a group of stiff yellow sete. There is 
moreover a second, similar group nearer to the median line, which appears to represent 
a second process, formed by a prolongation of the ventral margin of the penultimate 
segment. . 
Gervais + considers that these appendages should be compared to the branchial appen- 
dages in Neuroptera rather than to true legs; he observes, * Cette manière de voir, 
que nous avons proposée peu de temps aprés, rend également compte de l'absence de 
trachées déja constatée par plusieurs observateurs chez les véritables Thysanoures, c'est à 
dire, chez la famille des Lépismes." The branchial appendages of Neuroptera, however, 
are dorsal, while those of the Lepismidæ are ventral; moreover, in opposition to the 
above assertion, the Lepismidæ undoubtedly have tracheæ, although the system may not 
be very largely developed. 1t seems to me curious that there should be any difference 
of opinion on this point, because, from the transparency of the creature, the tracheæ in 
the legs are visible without dissection. It is true that Treviranus } was unable to satisfy 
himself as to the presence of tracheæ ; but I can only account for this on the hypothesis 
that he did not examine freshly killed specimens. 
The egg-tubes and the formation of the ovum resemble those of Petrobius, as described 
by me in the * Philosophical Transactions ’*. 
The posterior dorsal plate has a squarish termination. 
REPRODUCTION OF LOST PARTS. 
M. l'Abbé Bourlet, who was unfortunately ignorant of Mr. Templeton's memoir, gave 
as a character of his genus Heterotoma (a name which he subsequently changed for 
Ætheocerus), and which is composed of the species forming Templeton's genus Orchesella, 
that the segments of the antennæ varied from 2 to 5, those even of the same individual > 
being often dissimilar in the number of their segments. He was aware that M. Mac- 
quart regarded these differences either as abnormal or accidental; but he rejected this 
explanation because :—1°. Dans le cas où les antennes sont inégales, le dernier article de 
la plus eourte, quel que soit son rang numérique, n'est jamais conforme à l'article cor- 
respondant de l'autre antenne; 9. il affecte constamment une forme analogue à celle 
de l'article terminal, ou le cinquième ; 3°, il en est de méme pour les antennes égales, 
mais ayant moins de cinq articles; dans ce cas, le dernier est toujours plus gros et plus 
+ Suites à Buffon. Insectes Aptéres, vol. iii. p. 446. 
* Vermischte Schriften, Tab. ii. fig. 4. 
$ Phil. Trans. 1861, p. 619. 
t Vermischte Schriften, vol. i. p. 16. 
