370 WHEELER. [Vot. Ill. 
indicate that at one time they opened on the surface of the 
body, and that their orifices were subsequently carried in by a 
deepening of the proctodzal invagination. Possibly these tubes 
in insects are homologous with the anal tubes of the Echzurus 
larva, which are modified segmental organs. Gegenbauer (14) 
has intimated the possible derivation of the Malpighian vessels 
from paired tubes opening on the outer surface of the body. 
He says: “As they [the Malpighian vessels] are formed at 
the same time as that portion of the hind-gut, which in the 
embryo is developed from the ectoderm, it is not improbable 
that they primitively opened on the surface of the body, or were 
derived from organs which did so. In all divisions there are 
two chief canals, as is often seen at the point where a large 
number of canals open and unite. This number may therefore 
be regarded as a primitive character.” 
MILWAUKEE, Sept. 12, 1888. 
LIST, OF WORKS REFERRED) TO: 
1. Ayers, H. On the development of CGécanthus niveus and its Parasite 
Teleas. Memoir. Boston Soc. Nat. Hist. Vol. III., No. 8. 1884. 
2. Balfour, F. Treatise on Comparative Embryology. Vol. II]. 1881. 
3. Blochmann, F. Ueber eine Metamorphose der Kerne in den Ovarial- 
elern und iiber den Beginn der Blastodermbildung bei den Ameisen. 
Verhand d. naturh. medicin. Vereins zu Heidelberg. Bd. III. Heft 
3. 1884. 
4. Blochmann, F. Ueber die Reifung der Eier bei Ameisen und Wespen. 
Festschrift zur Feier des 100 jahr. Bestehens der Ruperto-Carola. 
Heidelberg. 1886. 
5- Blochmann, F. Ueber die Richtungsk6érperchen bei Insekteneiern. 
Morph. Jahrb. Bd. XII. Heft 4. 1887. 
6. Brandt, A. Ueber die Eirdhren der Blatta (Periplaneta) orientalis. 
Mém. Acad. St. Petersbourg. Sér.7. Tom. XXI. 1874. 
7. Bruce, A. T. Observations on the Embryology of Insects and Arachnids. 
Baltimore, 1887. 
8. Biitschli,O. Bemerkungen iiber die Entwicklungsgeschichte von Musca. 
Morph. Jahrb. Bd. XIV. Heft 1. 1888. 
g. Carnoy, J.B. La Cytodiérése chez les Arthopodes. ‘‘ La Cellule.” Tom. 
I. Fasc. II. 1885. 
10. Cholodkovsky, N. Ueber die Bildung des Entoderms bei Blatta ger- 
manica. Zoolog. Anzeig. No. 275. 1888. 
11. Emery, C. (Critical note on Korotneff and Grassi) Biolog. Centralbl. 
Bd. V. 1887. 
