170 CHIRONOMUS PEASINUR. 



I have not seen the least trace in this larva of the triangular 

 muscles known as the wings of the heart.* although I have 

 distinctly recognised them in the larva of a closely allied insect, 

 the Crane-Fly, where they extend nearly the whole length of the 

 vessel. The blood is admitted by two slits or orifices at the 

 posterior end of the chamber, and is prevented from returning by 

 two valves at its anterior end. This first chamber is much the 

 largest of the series, and seems pre-eminently to claim the title 

 of heart ; the rest of the tube may be more justly entitled' the 

 aorta. I can detect no other orifices for the admission of blood 

 except the two mentioned. 



The fatty rete of this larva generally presents a number of oil- 

 globules of very various sizes scattered through a homogeneous 

 ground-substance. In young larv?e I have found nuclei instead of 

 oil-globules. The latter, therefore, I think, must be looked upon as 

 the secretion of cells of which the whole substance was originally 

 composed, but the divisions between them have disappeared, the 

 structure having become what is termed a syncitium. It assumes 

 two forms, the first of which is a laminated trabecular one, 

 consisting sometimes of irregular sheets of rounded contour, one 

 or more of which may intervene between the hypoderm and the 

 muscular tunic of the larva, and connected with each other by 

 anastomosing processes ; or the trabecular character being more 

 pronounced, it may, as in the thoracic segments, consist of a 

 number of intercrossing and anastomosing shreds. Sometimes 

 portions are found between the muscles. The second form is 

 found surrounding the intestine, and consists of sausage-shaped 

 or irregularly tubular masses of the same tissue. As I think 

 there is always a distinction, more or less, between the portions of 

 the rete, I would propose to designate them respectively by the 

 terms : somatic rete and splanchnic rete. At other times I have 

 found the somatic rete largely composed of granular cells of very 

 varying sizes, up to r-8oo of an inch, with no oil-globules. This 

 seems to be a special condition, and the larvDs in which it is found 

 are so swollen out by the great accumulation of it in each segment 

 as to assume a knotted appearance. In this condition, too, it 



* Since writing this, I have l^een able to recognise the existence of the 

 triangular muscles. 



