380 BULLETIN: MUSEUM OF COMPARATIVE ZOOLOGY. 
EXPLANATION OF PLATES. 
All figures were drawn with the aid of the camera lucida from preparations of 
Thymalus marginicollis Chevr. The magnifications are given with the descriptions 
of the several figures. 
In Plates 1-5, Figures 1-5, 7, 9, and 11-are drawn from reconstructions of serial 
sections. They form two series of figures illustrating the anatomical changes of 
the dorsal antero-posterior (Figs. 1, 2) and lateral dorso-ventral (Figs. 3-5, 7, 9, 11) 
groups of metathoracic muscles during metamorphosis. These figures are all 
magnified 67.5 diameters. 
aa. Cohn 
GLE &; 
cd. n. 
Cis. 
cl, mit. 
el. tr. 
el. tr 
cl. tr.2 
a 
cp.adp. . 
CP carn 
COs oa: a 
dep. trg. . 
ely. 
e’stn. . 
e’th, 
ext. al. pa. mt’thz. 
ext. cox. mt’thx. (1-3) 
ext. trchn. mt’thx. . 
fix. al, mt’thx, (1-5) 
Six. cox. mt’thx. (1-5) 
ext. al. mag. mt’thx. . 
ABBREVIATIONS. 
Cohnheim’s areas. 
Wing. 
Nerve cord. 
Chromatin masses left after the disintegration of nuclei. 
Tracheal cells in stages of mitotic division. 
Tracheal cell. 
Tracheal cells showing connections with tracheae. 
Tracheal cells whose connections with the tracheae have 
been severed, but which show tracheoles through their 
cytoplasm. 
Tracheal cell entirely embedded in the muscle. 
Fat body. 
Heart. 
Cuticula. 
Tepressor tergi. 
Elytron. 
Musculus episternalis. 
Epithelial lining of the foreintestine. 
Extensor alae magnus metathoracis. 
Extensor alae parvus metathoracis. 
Extensor coxae metathoracis (primus, secundus, tertius). 
Extensor trochanteris metathoracis. 
Flexor alae metathoracis (primus, secundus, tertius). 
Flexor coxae metathoracis (primus, secundus, tertius, quat- 
tuor, quintus). 
