9O ALBERT FRANCIS BLAKESLEE. 



Absidia spinosa was first found by Lendner and is correctly 

 described by him (Lendner '08). Its zygospores agree with 

 other Absidias in possessing circinate outgrowths which develop 

 from the suspensor soon after the formation of gametes. It 

 differs from other Absidias, which it resembles in its method of 

 nonsexual multiplication, by being hermaphroditic (cf. right- 

 hand side of Fig. 8, Plate I.) and heterogamic (Fig. 4). Figs. 1-7 

 represent stages in development in living material drawn at the 

 times indicated in the legend. A considerable number of conju- 

 gations have been followed in living material and stages have 

 been studied in stained and mounted material. Unequal 

 gametes, such as are shown in Fig. 4, unite, as in Fig. 6, and the 

 zygote thus formed grows into a mature zygospore such as is 

 shown in Fig. 7. In moist chamber cultures, drops of fluid 

 generally accumulate around the uniting gametes (Fig. 6), often 

 causing appearance of transverse lines that suggest additional 

 cross walls. They can be distinguished from cross walls, how- 

 ever, by forcing the conjugating filaments against condensed 

 moisture on the under side of the cover-glass. Perhaps the most 

 typical form of conjugation is that shown in Fig. 8, where a 

 rather stout branch on the right has applied itself to the more 

 delicate termination of the main axis causing the production 

 from the latter of a small male gamete, while it produces from 

 its own enlarged tip a large female gamete. Curved outgrowths 

 arise from the swollen suspensor but are not produced from the 

 side of the smaller gamete. In Zygorhynchus a septum is regu- 

 larly formed across the main axis just above the origin of the 

 stout conjugative branch. This septum is as regularly absent 

 in Absidia spinosa. 



When for any reason the process of conjugation is arrested 

 after the formation but before the union of gametes, these sexual 

 cells may round themselves off, form thick walls and become 

 azygospores. This is brought about in greater or less degree 

 when the conjugating filaments in a moist chamber culture 

 become immersed in a drop of condensed water on the underside 

 of the cover-glass. Whatever the cause of the check to normal 

 conjugation, the size of the azygospores depends upon the size 

 of the gametes from which they develop. Thus in Fig. 33 it 



