THE PROBLEM 19 



of morphologically and physiologically well-defined and 

 usually multicellular individuals make up a relatively 

 persistent composite individual. Most plants and the 

 so-called colonial animal forms are good examples. 

 The individuals which make up a composite individual 

 are constituent individuals. These may be either parts 

 of a cell, different cells, or cell groups composing 

 organs. 



As regards the various axes of the axiate individual, 

 uniformity of designation is also highly desirable. The 

 polar, longitudinal, apico-basal, or antero-posterior 

 axis, as it is variously called, represents the primary 

 or major order when such an order is present in the in- 

 dividual. In cases where the axes of the individual 

 arise de now and are not simply carried over from pre- 

 existing individuals, this axis is apparently the first to 

 arise and other axes arise in relation to it. It is often 

 convenient, therefore, to call this axis the major axis of 

 the individual and the other axes minor axes. 



With reference to particular axes, we are accus- 

 tomed to distinguish position and direction according 

 to the general plan of the individual, the relation of 

 certain axes to others, the characteristic position, 

 behavior, or direction of movement of the organism. 

 The following terms are commonly used for this pur- 

 pose: apical and basal, distal and proximal, anterior and 

 posterior, peripheral and central, median and lateral, 

 dorsal and ventral, besides various others which refer 

 to particular regions, such as cephalic and caudal, oral 

 and aboral, etc. All these terms are useful in particular 

 cases, but greater uniformity and simplicity are desir- 

 able for purposes of general consideration. 



