12 



MORPHOLOGY OF THE CELL. 



fine-grained protoplasm forms the ground, so to speak, in which the spores are imbedded. 

 Afterwards each spore becomes more sharply defined, the clear space disappears (e), its 

 substance becomes more fine-grained and clearer ; and in one of its foci is formed a 

 vacuole, /. e. a transparent drop of fluid. Finally, each spore surrounds itself with a 

 firm membrane, the vacuole disappears, and in the centre is formed a large drop of 

 a strongly refractive oil, as well as numerous smaller drops of oil. 



D. Formation of Cells by Division of the Mother- Cell. — In the protoplasm 

 of a cell new centres of formation arise ; around each of these a portion of the proto- 

 plasm of the mother-cell gathers, 

 in order to form a new cell ; in this 

 manner the entire protopJasni of the 

 mother- cell is completely used up ; its 

 cell-wall alone remains, if it pos- 

 sess one, which is not always the 

 case. If the mother-cell has a 

 nucleus, this is usually dissolved in 

 the protoplasm ^ ; and as many new 

 nuclei are produced- as daughter- 

 cells originate ; or the nucleus of the 

 mother-cell di'vides into t^vo nuclei, 

 while the whole protoplasm sepa- 

 rates into tavo portions (see Han- 

 stein). 



ist Case. Cell - DiiHsion ^vith 

 Contraction and Rounding-off of the 

 Daughter-cells. 



a. A Cell-^vall is not secreted till 

 daughter-cells, already isolated, haue 

 becot?ie completely separate. An ex- 

 ample is afforded by the formation of 

 the oospores of Achlya (Fig. 8). At 

 the end of a sac-shaped cell or of 

 a branchlet of one, the protoplasm 

 collects, the larger end itself swells 

 up into a globular form [A, E), 

 and, by the formation of a sep- 

 tum (C), becomes an independent 

 cell (the oogonium). Nucleus-like 

 structures sometimes, but not usu- 

 ally, form in the protoplasm (as in C). The whole protoplasmic body then breaks up 

 into two, three, four, or more parts, which very quickly round themselves off into a 

 perfectly spherical form; (in a large number of observations I have never seen an 

 intermediate form between C and Z).) The parts thus formed {e, e in Z)) contract 

 violently during their separation ; i. e., their protoplasm becomes denser by expulsion of 



Fig. 8. — Oogonia and antheridia of Achlya lignicola, growing on wood 

 in water ; the course of development is indicated by the letters A — F. a 

 the antheridium, b its sac penetrating into the oogonium (X550). 



^ An exception occurs in the formation of spores of Anthoceros, where the nucleus of the mother- 

 cell is not absorbed until four new nuclei are formed. 



^ In Spirogyra, Mougeotia, and Craterospermum, the new nuclei only arise during the progress 

 of the division of the protoplasm (De Bary, Die Familie der Conjugaten, Leipzig 1858). In the 

 formation of the stomata of Hyacitithiis orie?italis, I was unable either before, during, or immediately 

 after the division of the mother-cell, to perceive a nucleus; it did not appear in any of the deriva- 

 tive cells until a considerable time after the division. 



