Timhcr-lahe — Swarm-Spores of Hydro did yon. 489 



Strasburger (25) has recently discussed very fully the 

 question as to the structure and homology of the cilia bearing 

 organs of the swarm spores of such forms as Cladophora, Vau- 

 cheria and Oedogoniuin. He thinks that there is a simple 

 swelling of the plasma membrane at the point of insertion of 

 the cilia, and that this is neither a centrosome nor the equiva- 

 lent of the blepharoplast. Strasburger contends that the entire 

 "mouth piece" of the swarm spore of Oedogoniuni is to be re- 

 garded as the homologue of the cilia bearing band of the an- 

 therozoids of the Gymnosperms and ferns. 



Dangeard (7) has attempted to establish homologies be- 

 tv/een the structure of the swarm spores and gametes of the 

 Clilamydomodineae and Polytoma uvella, and the spermatozoa 

 of the higher animals. But he fails to show that the develop- 

 ment of the structures that he thinks are homologous is in any 

 Tvay similar. 



The main features in the morpholog}^ and reproduction of 

 Hydrodictyon have become well known through the researches 

 of Vaucher (3), Areschoug (1), Braun (4), Pringsheim 

 (20), Suppanetz and others. A very complete historical ac- 

 count of these researches is given in Artari's (2) paper re- 

 ferred to beloAV, so that I shall take account of those papers 

 only that have a direct bearing upon the problems here inves- 

 tigated. The most accurate and complete account given by 

 the earlier observers of the cell structure and method of spore 

 formation was that of Braun ((3). 



According to this observer the protoplasmic contents of the 

 cell consist of three distinct layers: 1. The "primordial 

 membrane," a thin, somewhat opaque layer appearing finely 

 punctate which is dravxTi away from the cell membrane by the 

 action of acids. 2. An outer "mucilaginous" layer, which is 

 thicker than the preceding, but thinner than the following 

 layer. It appears to be irregular on the outer and inner sur- 

 faces and contains numerous "mucilage granules" (nuclei ?) 

 which are som.ewhat large and irregular in outline. 3. "In- 

 ner mucilaginous laver" — the thickest laver of the three con- 

 taining the chlorophyl which in young or poorly developed cells 

 appears in irregular rows of small granules forming a network, 



