THE MASTIGOPHORA 



129 



are composed, for the most part, of descendants of one ancestor and 

 are formed by incomplete division or by subsequent attachment. In 

 these colonies, which are wonderfully varied, the individual monads 

 in some cases are embedded in a transparent cellulose jelly secreted 

 by the cells, and in which they lie freely, or attached to one another 



Fig. 73. — Division of Gonium pectoralc O. F. M. 

 a, 6, and e, undivided cells ; c, d, f, k, and /, 4-celled stages ; h, i, j, n, o, 8-celled stages ; g, 

 m, and/, 12-16-celled stages. 



by stalks, while in other cases there is no surrounding matrix, the 

 individuals remaining connected through incomplete division or by 

 attachment subsequent to division. Gonium (Fig. 72), Pandorina, 

 Uroglena, Proterospongia, Volvox, etc., have the cellulose jelly, while 

 Dinobryon, Anthophysa, etc., are formed by attachment subsequent to 

 division. In some of the more complicated colony-forms, especially 

 in the Phytoflagellida, the adult condition is attained through cleavage 

 stages as regular as in any metazoan egg. The formation of such a 



