-O CLAYPOLE. [Vol. II. 



The eggs all undergo equal holoblastic cleavage, resulting in a 

 uniform single-layered blastoderm soon rendered many layered 

 by rapid growth. The surface becomes crenated and ridged 

 and forms a cuticle, also crenated. The blastoderm becomes 

 smooth, and outlines of the embryo appear. The second em- 

 bryonic layer is said to arise from a definitely placed area 

 lying between the head and tail of the belt-like germ band. A 

 "dorsal organ" is probably present, though not described as 

 such. Nine pairs of apjDcndages appear: antennae i, mandi- 

 bles I, maxillae 2, thoracic legs 3, abdominal 2. One pair of 

 those on the abdomen forms the collophore, and the other the 

 spring. Poduridae are found to resemble the lower arthropods 

 in the following respects : (i) holoblastic cleavage ; (2) absence 

 of amnion; (3) possession of blastodermic cuticles; (4) the 

 ■ formation of the intestine from the middle germ layer. 



In 1882 Lemoine ^ added studies on the Collembola yi;^?/r^- 

 phonis laricis and SniintJuints plumbcns, two species differing 

 widely from each other in habits and form. The first is small, 

 springless, inactive, and colonial, while the second is large, 

 with a well-developed spring, active, and solitary. The eggs of 

 Anurophorus found in April and May were clear and easy to 

 observe, while those of Sminthurus found in November and 

 December were slow in development and difficult to study. 

 Superficial cleavage, accompanied by secondary yolk cleavage, 

 was true of the former, and the latter showed very unequal 

 holoblastic cleavage with a blastoderm early formed of two 

 layers. "Dorsal organs" appear in both, persisting up to the 

 time of hatching. The entoderm is said to arise from two in- 

 pittings, one in front and one behind the " dorsal organ " and at 

 several other places on the periphery. The germ band, at first 

 forming a belt surrounding the whole circumference of the 

 ^^g, shows 12-13 segments : i cephalic, 3 mandibular, 3 tho- 

 racic, and 5-6 abdominal. Two membranes appear, one of 

 which is clearly connected with the "dorsal organ." A collo- 

 phore develops in both forms, but the spring is rudimentary in 

 Anurophorus, a condition also true of the tracheal system. 



^ Lemoine, P., " Recherches sur le Developpement des Podurelles," Ass. Franc, 

 p. advanc. des Set. La Rochelle. 1S82. 



