46 ] The Classification of Lower Organisms 



fertilization. Oltmanns (1898) disproved this: he showed that the nuclei of auxiliary 

 cells are inert, and that the nuclei of carpospores are derived entirely from zygote 

 nuclei. Yamanouchi (1906) showed that the chromosome number of carposporic 

 individuals of Polysiphonia violacea is 10, and that that of tetrasporic individuals is 

 20; and reported much more of the cytology. Centrosomes appear de novo during the 

 earlier stages of mitosis, and fade out and disappear during the later stages. The 

 mitotic spindle is formed, and the chromosomes take their place upon it, within an 

 intact nuclear membrane, which fades out in later stages. In meiosis, which produces 

 the nuclei of tetraspores, the tetrads and diads divide within the original nuclear 

 membrane, which becomes tetrahedrally lobcd, and then disappears except where 

 the haploid groups of chromosomes lie against it, with the result that the membranes 

 of the tetraspore nuclei are partly old and partly new. 



There are some 2500 species of Heterocarpea, including comparatively few in 

 fresh water, but the majority of the marine algae. Many of them are beautiful; their 

 variety and beauty contribute to the pleasure which people find on coasts. Exper- 

 ienced naturalists can identify many genera by gross structure, but the systems of 

 orders and families based on gross structure, such as those of Kiitzing (1843) and J. 

 Agardh (1851-1863), have been found artificial and abandoned. A proper respect 

 for the principles of nomenclature makes it necessary, however, to apply many of the 

 names used in these systems. Schmitz applied his morphological studies to a classifica- 

 tion of the typical red algae as four groups ( 1889) ; Engler ( 1897) made these groups 

 definitely orders. Subsequent scholars have found this system sound in principle, but 

 have found it necessary, on the basis of studies of additional examples (for example, 

 by Kylin, 1923, 1924, 1925, 1928, 1930, 1932; Papenfuss, 1944; Sjostedt, 1926; 

 Svedelius, 1942) radically to rearrange the families and genera. At least four orders 

 in addition to those of Engler have been proposed but reductions have decreased 

 the number currently recognized to six. 



The following key to the orders is a rather considerable modification of those pub- 

 lished by Kylin (1932) and Smith (1944). 



l.All free-living individuals haploid; tetra- 

 spores not produced, or produced as carpospores. . Order 1. Cryptospermea. 

 1. Free-living individuals of two types, the one 

 producing gametes (the zygotes giving rise 

 to carpospores), the other producing tetraspores. 

 2. Without specialized auxiliary cells or 

 nurse cells, the lower cells of the carpo- 

 gonial filaments, or normal vegetative 



cells, serving as auxiliary cells Order 2. Sphaerococcoidea. 



2. With specialized nurse cells, the carpo- 

 spores produced from filaments which 



have made contact with these Order 3. Gelidialea. 



2. With specialized auxiliary cells from 

 which the carpogonia develop. 



3. The auxiliary cells being intercalary 

 cells in specialized filaments homol- 

 ogous with the carpogonial filaments. . . . Order 4. Furcellariea. 

 3. The auxiliary cells terminal in fila- 

 ments which grow from the support- 

 ing cells of the carpogonial fila- 

 ments before fertilization Order 5. Coeloblastea. 



