1885.] 



MICROSCOPICAL JOURNAL. 



233 



lows. Its further history is not 

 known. 



[The oval or spherical cells, which 

 may or may not be surrounded by 

 thick, lamellose, hyaline envelopes, 

 are arranged in a linear series within 

 a tubular, hyaline, gelatinous C3'lin- 

 der (or vesicle, as Reinsch designates 

 it). The cells are full to repletion 

 with green, granular contents. Im- 

 mediately after division the cells are 

 in contact, and therefore truncate in 

 form. Propagation by swarm spores 

 has not been observed. Compare 

 Hormospora^ i6. 



The cylindrical sheath is closed at 

 both ends, the upper end rounded, 

 sometimes expanded, with several 

 green cells in the club-shaped in- 

 terior ; the lower end is narrowed 

 and attached.] 



78. Genus Sphceroplea Agardh. 



Filaments composed of long, cylin- 

 drical cells, which, in the vegetative 

 condition, have green, protoplasmic 

 contents, which is divided by large, 

 I'egularly placed vacuoles, into a num- 

 ber of equidistant rings or bands. 

 The vacuoles are enclosed in a mem- 

 brane, and the single cells appear, 

 therefore, to be divided by false septa. 



All vegetative cells are transformed 

 into sexual organs. Oospheres num- 

 erous in a mother cell, of a dark 

 green color. The oospores, after 

 fertilization, produce three mem- 

 branes, the outer of which is thrown 

 off, leaving a colorless, widely sepa- 

 rated, longitudinally or irregularly 

 wrinkled or plaited epispore, a color- 

 less close-lying endospoi'e, and red 

 contents. 



The spermatozoids are formed in 

 innumerable number by the division 

 of other vegetative cells into yellow 

 portions ; they are yellow, elongated, 

 with a thick hinder end, a beak-like, 

 colorless anterior portion, with two 

 cilia, and escape through openings 

 formed in great number in the wall 

 of the antheridium, and find their way 

 to the oospheres. • 



The zoospores coming from the 

 oospores are spherical, cylindrical or 



pear-shaped form, carmine-red or red 

 and green, with hyaline end and two 

 cilia. 



[The contents of the cells some- 

 times appears quite frothy from the 

 numerous vacuoles, especially just 

 previous to fructification.] 



Fixing arranged Diatoms and Sec- 

 tions. 



Among the many methods of fix- 

 ing diatoms and other minute objects 

 upon a slide or cover-glass, the method 

 of M. Threlfall has been very highly 

 commended. The diatoms are ar- 

 ranged upon a perfectly dry surface 

 of caoutchouc spread upon the slide, 

 and fixed in place by application of 

 gentle heat. The details may be 

 briefly given as follows : — First pre- 

 pare a solution of caoutchouc in 

 benzene, adding sufficient caoutchouc 

 to produce a jelly-like mass. Of this 

 take a portion as large as two peas, 

 and dissolve it in thirty cubic centime- 

 tres of benzene. This dilute solu- 

 tion is the one that is used. Crude 

 caoutchouc should be used, or such 

 as has not been vulcanized. 



This solution aiiords an easy means 

 of attaching thin sections in series 

 as well as diatoms to a glass slip. In 

 either case the slip is coated with a 

 thin layer of caoutchouc by flowing 

 it with the solution as a photographic 

 plate is coated with collodion. The 

 solvent rapidly evaporates, leaving the 

 caoutchouc in a thin film on the glass. 

 The sections, ordinarily included in 

 paraffin, are arranged in series on the 

 caoutchouc. The slide is then 

 warmed to a temperature of 56 -60^ 

 C.,when the caoutchouc softens, and 

 the sections become fixed in place. 

 The paraffin is then removed by petro- 

 leum spirit, and if it is desired the sec- 

 tions may be stained in position. 



To attach diatoms it is only neces- 

 sary to arrange them on the layer of 

 caoutchouc and warm gently. 



This method of fixing diatoms is 

 highly commended by P. Francotte.* 



• Bull. Soc. Beige de Micr. 



