2 W. Hofmeister on the Propagation 



ganisms, in a boggy locality near Leipsic, exhibited numerous 

 conjugated specimens. The conjugated individuals displayed 

 exactly the behaviour w^hich Ralfs* has represented and Al. 

 Braunf described of those of Cosmarium margaritiferum. The 

 Cosmaria which had commenced the conjugation-process ap- 

 peared cracked apart at the constricted place in the middle. 

 Into each of the halves of the tuberculated cell-coat of the two 

 mother-individuals, extended a continuation of the membrane 

 of the conjugation-cell. This smooth membrane completely 

 lined the interior of the tuberculated half-shells. The contents 

 of the conjugation-cell revealed no definite arrangement ; they 

 were mostly accumulated in the middle into an irregularly- 

 shaped ball; in other cases separated into several such balls, 

 part of which extended even into the split half-shells of the 

 mother-cell (PI. I. fig. 2). With these conjugated individuals, 

 in the same fluid, occurred (very sparingly) particular specimens 

 which bore, in the middle space between the two separated half- 

 shells, a broad, delicate-walled utricle, the circumference of 

 which about equalled that of the two half-cells taken together. 

 The arrangement of the cell-contents in the primary portions of 

 the cell did not appear essentially altered ; the contents of the 

 intermediate expansion consisted of a thick coat, upon the wall 

 of granular protoplasm with sparingly scattered chlorophyll 

 (fig. 1). This condition is probably that which immediately 

 precedes conjugation J, originating by excretion of new cellu- 

 lose at the deepest part of the constriction, after the cracking 

 of the membrane and separation of the primary halves of the 

 cell, exactly as in normal cell-division, from which this process 

 can only be distinguished by the omission of the formation of a 

 septum at the narrowest part of the isthmus. Similar phaeno- 

 mena have been observed by Nageli in Cosmarium crenulatum^, 

 and by Mrs. Herbert Thomas || in Cosmarium margaritiferum 

 (scarcely specifically distinct from C. tetraophthalmum) , only that 

 here the intermediate piece of the Alga did not conjugate with 

 the similar piece of another individual, but, producing tubercles 

 on its outer surface, continued the vegetative life. 



In other conjugation- cells there lay in the middle part of the 

 conjugation-cell, a globular cell enveloped in a rather thick 

 membrane, of gelatinous aspect, and smooth on the outside (the 



* hoc. cit. pi. 16. fig. 2 d. 



t Verjiingung, p. 315 (Ray Translation, p. 295). 



X Vide Nageli, Gatt. einz. Algen. Zurich, 1849, p. 118, pi. 7- fig. ^9, 

 Cosmarium rupestre. 



§ Gatt. einzell. Algen, p. 118, pi. /. fig. 7b. 



II Quarterly Journal of Microscop. Science, iii. p. 35. pi. 5. figs. 17, 18 

 (1865). 



