KONGL. SV. VET. AKADEMIENS HANDLINGAR. BAND 



26. 



n:o 



19 



I have examined some living frustules of A. complexa. It has along the ventral side a single 

 cjromatophore-plate enclosed in a plasmatic mäss, from which fine plasma-threads radiate towards 

 the walls. 



ii. complexa, 500 times magnifled. 



A. incerta, 500 times magnified. 



\^0:y ^ 



Of A. incerta I liave had an opportiinity of examining niimerous living specimens. This species 

 lias also a single chromatopliore-plate along the ventral side of tlie zone, enclosed in a plasma-mass 

 which sends fine plasma-threads to the walls of the frnstule. 

 If the living frustules be suddenly killed by a boiling con- 

 centrated solution of mercuric chloride in alcohol, and then by 

 washing freed from mercuric salt, they may be stained with 

 diiferent dyes. Carmine colours the nucleus, which is placed 

 above the plate and on its centre. Stained with chrysoidine 

 numerous granules in the plasma-mass take an intensely yellow 

 colour, and are probably elpeoplasts, as fatty matters are intensely 

 coloured by the dye. 



Änricula minuta has also a single chromotophore-plate 

 along the ventral side, and at the primordial stratum of the 

 plasma a number of small granules, possibly geline-secreting 

 organs. 



Auxospores. In Å. minuta a single globular auxospore is 

 formed ont of two frustules. In the annexed sljetches a and c 

 represent a frnstule in living state, h a frnstule in the state of 

 division. Fig. cl shews two frustules enclosed in a mucous mäss, 

 the first stage of the conjugation. In e the auxospore is formed 

 and enclosed between the empty valves; f seems to represent an 

 mature auxospore, and g two frustules, to judge from the size, 

 probably formed out of the auxospore. 



Some extreme forms of Auricula have a very peculiar 

 appearance, but by intermediate steps they are connected on one 

 hand with Amphiprora, on the other with Amphora, so nearly 

 indeed that no line of demarcation may be traced between Am- 

 phora and Auricula. 



All species of Auricula are marine and pelagic. Some 

 forms are thin and membranaceous. Otliers have strong valves, 

 but thin connecting zones, so that entire frustules are rarely to be found in gatherings which 

 have been cleaned by means of acids. 



A. minuta, 500 times maguified. 



