346 BIOLOGY OF THE PROTOZOA 



With contraction of these threads, form and vohime changes 

 result in hydrostatic accommodations such that the organism rises 

 or falls in the water. 



Fig. 152. — Lichnaspis giltochii, one of the Actipylea. The spines of strontium 

 sulphate are arranged in accordance with the " Millleriau law" as follows: a, a, a, a, 

 northern polar; b, b, b, b, northern tropical; c, c, c, equatorial; d, d, d, d, southern 

 tropical; and e, e, e, southern polar. (From Calkins after Haeckel.) 



In many cases the spines are bound together by a latticed skeleton 

 consisting of twenty plates, each plate formed as an outgrowth from 

 a spine. Other peculiarities of this Order are found in the thinness 

 of the capsular membrane, frequent intracapsular yellow cells, 

 and definite axopodia in addition to the usual rhizopodia. 



