Nov.. nao.] r. KUWjWA.—SOMK PKCULIAUrrmS OBSERVED. 355 



KuSANo'^ pointed out the biological significance of the 

 chcmotactic activity of the swarmspores of Mr-voynycctcs, which 

 responded positively to all the agents used giving the acidic 

 projiertv, upon the havitat of this organism on the rotten wood 

 or decaying plant tissues, where the presence of acidic substances 

 was proved by him. In the case of the present Chlamydomonas 

 it is little known as to its habitat in natui'e, and it is difficult 

 at present to get a precise knowledge on the biological import- 

 ance of the chcmotactic activity toward the acids. It may, 

 however, throw some light on this point, when we call the fol- 

 lowing note on the source of this organism in mind : — 



Very minute samples of Porphyra tenera were taken from the sea in condition 

 growing on tlie dead branches of trees, or " Ilibi " as popularly called among the 

 people with us, which were planted artificially at the bottom of the littoral region of 

 the sea to uet a good vegetation of Porphyra growing thereon. A piece of the branch 

 was put into the artificial sea water in various kinds of combination of its constituents 

 and with various sorts of scmrce of niti'Ogen or without them. The culture continued 

 from the beginning of January to the end of March. During tlie experiments tiie 

 culture-media were replaced once a week. After the experiments had come to end, 

 the culture-media were left without care. In the middle of April it was found to 

 my astonishment that a culture-medium witli ammonium chloride as the source of 

 nitrogen became green on tlie side away from the windrow. This was diagnosed to 

 be swarmspores of a species of Chlamydomonas, and the pure culture was tried. It is 

 unknown wiience the organism came, but it may be suggested that the spores came 

 with a branch of " Hibi/' whicli was covered otherwise with Ulva, Enieromorpka, 

 Diatomes, and other lower algae and animals together with rotten substances. 



The importance of this chcmotactic response of Chlamy- 

 domonas is considered to rest thereupon, that the N-source 

 from the rotten substances may be accompanied with acids in 

 the w'ay of decomposition or as its byproducts"' such as amino 

 acid, carbonic acid, phosphoric acid, etc.,^^ especially when we 

 bear in mind that the organism can not propagate, as has 

 been actually proved to be the case, in the medium without 

 any trace of N-source, which may have no attractive power as 

 be the case with ammonium chloride or potassium nitrate. 



1) Journ. Coll. Agr. Imp. Univ. Tokyo. Vol. 2. 1909. 



2) Hydrogen sulphide, one of the decomposed products of protein substances is 

 also weakly acidic being soluble a little in water. 



3) JosT, L. Vorlesungen iiber Pflanzenphysiologie. 1908. 



