308 NEW YORK STATH MUSEUM 
This led him to study cross sections of the caudal spines, in 
which he found five cavities, two pairs above and a single large 
unpaired cavity below, which he thought opened near the tip.! 
From this he was led to conclude that the larvae, after insert- 
ing their caudal spines into the tissue of the plant, were able 
to draw the air in through this opening, through the ventral 
cavity of the caudal spines, and thence into the tracheal sys- 
tem and that there were no openings in the so called spiracles at 
the base of the spines. If Schmidt-Schwedt had studied the rela- 
tion of the tracheal system to the caudal spines, he would have 
seen the fallacy of his conclusions. As I have pointed out above, 
this cavity is lined with hypodermis, does not connect in any way 
with the tracheal system, and is closed at its base by a thick 
layer of hypodermal cells [pl.28, fig.8w]. If plate 28, figure 2, is 
examined, it will be noted that there is a line, vv, extending 
almost the entire length of the spine, which marks the ventral 
boundary wall of the paired ventral cavities, pve, which are 
strongly chitinized and can be readily seen through the exterior 
of the spine when it is studied in optical section. It was the 
apex of this cavity which Schmidt-Schwedt mistook for an open- 
ing. 
Dewitz? in 1888 published a short paper on the structure borne 
by the eighth abdominal segment in Haemonia equisetl, 
in which he maintains that there are no openings in the caudal 
spines and that the structures at the base of the caudal spines 
are open spiracles directly continuous to the tracheal system. 
1Though Schmidt-Schwedt figures such an opening, yet I reproduce his 
own description as a proof that he never saw such an opening. “ Bei 
mikroskopischer Betrachtung des ganzen Anhangs kommt man zu der 
Auffassung, derselbe sei einfach hohl und auf der Unterseite in seiner 
ganzen Liinge mit einem Liingspalt versehen. Querschnitte zeigten, dass 
dies ein Irrthum und dass der innere Bau ungleich verwickelter ist... 
Der 5te unpaare Kanal ist hohl und von zarterer Wandung umgeben; auch 
auf der Unterseite ist er geschlossen. Nach der Spitze zu verjiingt er sich 
mehr und mehr und hort noch vor derselben ganz auf. Hier muss er offen 
sein. Zwar habe ich das an Querschnitten mit vollstiindiger Sicherheit 
nicht festsellen kénnen, ebenso wenig wie das Gegentheil, aber es ergiebt 
sich das Erstere aus dem Umstand, dass sich dieser Kanal und zwar nur 
dieser beim Hinlegen in Paraffin oder Stearin stets alsbald véllig mit der 
Kinbettungsmasse anfiillte. Berl. Ent. Zeit. 1887. 31:328-29 
2Dewitz, Dr H. Berl. Ent. Zeit. 1888. 32:5-6. 
