OF DENISON UNIVERSITY. 21 



that this chamber was that in which the blood-corpuscles (or, better, 

 lymph- cells) were formed. The rectum is covered with irregular 

 masses of cells of varying size, and I more than once thought to have 

 observed their change to lymph-cells. It was impossible, unfortu- 

 nately, in the time allotted to observe the development of the circu- 

 latory system, but it would seem that the heart differentiates from the 

 connective tissues between the stomach and the scutum. 



(Fig. 3 illustrates not only the formation of the posterior appendic- 

 ular segments, but the rectal sinus with its muscles and lymph-cells. 

 A simple valvular apparatus separates the rectum from the anterior part 

 of the digestive tract. ) 



The next stage is illustrated on Plate VI, Fig. i. A change in 

 proportion and in size is all that requires notice. Figures ;^-6, illus- 

 trate the growth of the appendages. Fig. 3 is the first foot of the 

 right side of an individual over 1.5 mm. long. Fig. 4 is the same of 

 a younger individual of which Fig. 5 is the sixth and Fig. 6, the ninth 

 foot. Fig. 7 shows how the matrices of the caudal spines are devel- 

 oped from enlarged cells as are the corresponding parts in Daphnia. 



Fig 2, of Plate VII, illustrates the general characters of the animal 

 when about 2 mm. long. The maxilla have become larger and the 

 feet begin to assume their definitive form. 



Fig. 3 shows the growth of the caudal stylets and the character of 

 the valve at the opening of the anus, as well as the prolonged matrix 

 at the setae. Fig. 4 illustrates the differentiation of the optic lobes 

 and of the anterior part of the stomach. The heart is by this time 

 well formed and whatever part the rectal cells may have played in 

 originating lymph-cells, is lost. The liver lobes grow out from the 

 stomach and the labrum becomes reduced. The antennae now un- 

 dergo a rapid and remarkable transformation. In the male the shorter 

 ramus becomes atrophied as shown in Fig. 10, and from the base an 

 epipodal body is formed just as in the case of the feet. At first this 

 pouch resembles homologous organs in the feet, but soon it alters and 

 becomes greatly modified. In the female the change is similar, save 

 that this branchial sac fails to develop (Fig. 9.) The palpus of the 

 mandible is likewise reduced to a mere rudiment (Fig. 8.) 



The sexual organs of the female appear as lobed glands 

 (Fig. 12.) The caudal stylets are of considerable size. A 

 male, in the stage above mentioned, measures 3.5 mm. In the 

 following stages growth is rapid. The antennae modify rapidly. 



