183 



a formation is known as a "basket". It is completely formed in larvae 300— 

 400 iim long. The width of the "basket" base is three-fourths of its height 

 (Figure 135). The length of the larvae is 250-300 |j.m. 



Pluteus II Stage 



New arms, the posterodorsal, which also have a complex fenestrated 

 structure, appear as two small triradiate rods lying at the base of the postoral 

 arms. From the time of their appearance, the pluteus enters stage II. In this 

 stage the rudiment of the dorsal arch of about 120°C develops above the 

 stomach. From the posterodorsal rods, small secondary transverse rods are 

 directed inward. At this time, the first granules of crimson pigment begin to 

 appear at the tips of the arms. The length of the larva increases up to 500— 

 600 |im (Figure 136). 



Pluteus III Stage 



The preoral arms appear in stage III; their supporting rods are 

 simple because they are extensions of the dorsal arch. E. parma have 

 neither pedicellariae nor ciliated spaulettes. The epidermal vibratile plates 

 form between the posterodorsal and postoral arms. By the 7th— 8th day of 



Figure 135: Echinarachnius parma. Pluteus I stage. 



A — general view of the larval skeleton; B — basket structure. 



Legend same as in Figure 109. 



