106 F. BATES ON SEXUALITY IN THE ZYGNEMACE.E. 



diameter ; as a rule the two conjugated threads are equal, or 

 may vary to a slight extent on either side. As to the second 

 point, that the portion of the conjugating canal contributed by the 

 so-considered germ cell is shorter and wider than that contributed 

 by the sperm cell ; the suture marking their point of union will 

 consequently show nearest the spore-containing cell. This con- 

 clusion has evidently been arrived at from observations made at 

 the early stage of conjugation, and before the commencement of 

 the passage of the contents of the one cell into the other. At 

 this stage it is true that the tubular protuberance put forth by the 

 so-considered sperm cell does, when it comes into contact with the 

 opposing protuberance, force slightly inward the opposing face ; 

 but this I take to be but transitory, for afterwards there is doubt- 

 less resorption of the opposing membranes with fusion of the 

 tubular walls, so that a perfectly open channel of communication 

 is formed. When this is effected, and not till then, in my ex- 

 perience, does any passage of the contents of the one cell to the 

 other begin to take place. Then also it will be seen that the 

 shortening and widening of the so-considered germ-tube was only 

 due to the temporary pressure exercised upon it by the sperm-tube ; 

 for, when all is completed, the suture resulting from the fusion of 

 the two portions will be found, as a rule, in the middle ; although, 

 as might reasonably be expected, it is sometimes met with nearer 

 the one cell, and at others nearer to the other.* 



On point 3. That the protoplasmic contents of the cells in con- 

 jugating always travel in one direction. It is doubtless the rule 

 that in scalariform conjugation, the one thread parts with, and the 

 other receives the contents of the cells ; but this fact is so over- 

 borne by others as to be deprived of all its significance as a test 

 for sexuality. Spirogyra orbicularis, longata, insignis, Weberi, and 

 tenuissima, I have found in both scalariform and lateral conjuga- 

 tion ; whilst it is also a fact that both forms of conjugation may be 

 going on together in different parts of the same threads. To my 

 mind this settles the question ; for it must not be forgotten 

 that Mr. Bennett abandons all idea of sexuality in threads con- 

 jugating laterally ; and yet, really, this form of conjugating is 

 nearly as common as the scalariform. It is strange that Mr. 



*The appearance produced -when looking down through the conjugating 

 tube (when fractured at the suture) is due, iu my opinion, to its unequal 

 diameter ; it is rarely perfectly cylindrical : similar to what is seen in the 

 " bordered <pits " in the woody tissues of the Pines. 



