308 NEW YORK STATE 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 relar 

 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 [pi. 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, pvc, 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 equiset.l, 

 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. 



iThough, Schmldit-Sclawedt figures such an opening, yet I reproduce his 

 own description as a proof that he never saw such an opening. " Bei 

 miljroskopisoher Betrachtung des ganzen Anhangs kommt man zu der 

 Auffassung, derselbe sei einfach hohl und auf der Unterseite In seiner 

 ganzen Lange mit einem Langspalt viersehen. Querschnitte zeigten, dass 

 dies ein Irrthum und dass der innere Bau ungleieh verwickelter ist. . . 

 Der 5te unpaare Kanal ist hohl und von zarterer Wandung umgeben; auch 

 auf der Unterseite ist er geschlossen. Nach der St>itze zu verjiingt er sich 

 inehr und mehr und hcirt noch vor derselben ganz auf. Hier muss er often 

 sein. Zwar habe ich das an Querschnitten mit vollstandiger Sicherheit 

 Bicht festsellen konnen, ebenso wenig wie das Gegentheil, aber es ergiebt 

 sich das Erstere aus dem Umstand, dass sich dieser Kanal und zwar nur 

 dieser beim Binlegen in Paraffin oder Stearin stets alsbald vollig mit der 

 JEinbettungsmasse anfiillte. Berl. Ent. Zeit. 1887. 31:328-29 



2D€witz, Dr H. Berl. Ent. Zeit. 1888. 32:5-6. 



