The First Abdominal Segment of Embryo Insects. ”107 
dissociated and are ultimately to be regarded as blood cells, or whether 
they, in part at least, unite to form a loose tissue [lockeres Gewebe.] ” 
Graber has also observed the atrophy of the pleuropodia of Melolontha. 
Degeneration begins about eight days after the pleuropodia attain their 
maximum size. “ In the embryo thirty days old, with the dorsum closed 
over and the cephalic and anal ends already strongly flexed towards each 
other, the organ has diminished in size, not only when compared with the 
legs, but absolutely. More striking, however, is the reduction of the ab¬ 
dominal appendages in the thirty-four day old embryo, which in conse¬ 
quence of its great increase in length, is already completely coiled up and 
has attained to maturity. Here the appendages in question, are nothing 
but minute scales, hardly as long as a segment, and half concealed in the 
aforementioned eoagulum. They separate from the body with the slight¬ 
est touch. Probably they are pushed off while the insect is leaving its en¬ 
velopes, perhaps in consequence of rubbing against the same. In the 
hatched larva only the healed [verloethete] cicatrice of the peduncle is to 
be found.” 
Meloe proscarabceus. L. 
After treating of the formation of the germ-layers of this Coleopteron 
in a former paper, Nusbaum devotes a more recent article [’89] to a de¬ 
scription of the very interesting pleuropodia. I quote his description in 
extenso: 
“ The appendages of the first abdominal segment have up to the eighth 
day of development the form of roundish cylindrical sacks and consist, 
like the thoracic legs, of a single layer of cylindrical ectoderm cells sur¬ 
rounding a cavity in which may be seen a few loose mesoderm cells. On 
the eighth day of development each of these appendages differentiates into 
two parts: one basal and cylindrical, and one distal, which is spherical and 
somewhat pointed at the pole [outer end]. In the basal part the cavity 
persists as before, together with the loose mesoderm cells; in the spherical 
portion, however, the cavity disappears and is replaced by large and much 
lengthened cylindrical cells. These large cells arise by a kind of invagin¬ 
ation of a portion of the ectodermic layer at the pole of the appendage. 
The cells of the invaginated portion grow very rapidly and soon take on 
the appearance of very large and characteristic elements, so loosely juxta- 
posited that narrow clear slits may be observed here and there between 
them. The edges of the invagination approach one another till there re¬ 
mains only a small aperture leading into a roundish cavity closed on all 
sides. On the tenth day of development the segmentation of the thoracic 
legs may be seen very distinctly; in each leg three to four parts, or seg¬ 
ments may be distinguished, which are marked off by constrictions on the 
outer surface of the ectoderm. It is interesting to note, that the append¬ 
ages of the first abdominal segment seem also to undergo a kind of con¬ 
striction, so that I cannot concur in Graber'’s statement that “ the abdominal 
