ANIMAL NATURE OF DIATOME.E. 438 



many times seriate, it becomes extremely difficult to 

 convince one's self that the partial tubes are absent, and 

 the presence of external spermatia is really in accordance 

 with that absence. 



From the Lenormand I also received, under the name 

 of Schizonema Grevillei, inapplicable to it, another very 

 beautiful species, with very fine short threads, in which 

 the Naviculas are not only still shorter (0*017 millim.) but 

 also narrower (0-0045 millim.) and very acute. 



Monnema rutilans, Ag., (Schizonema.) 



In authentic specimens from Kiitzing and Jiirgens, I 

 find the length of the Naviculae 0*025 millim., and their 

 breadth only 0'004. Kiitzing says their length is ^" or 

 0'027, with the usual contradiction of a much smaller 

 figure. In this the Naviculae are only 7 '7 millim., which, 

 with a power of 420 corresponds to 0-018. 



I have no specimens of the two forms which Kiitzing 

 considers to be varieties of the preceding, with the names 

 S. parvulum, S. lubricum. 



Monnema Hoffmanni, Ag.; (Schizonema.) 



In a specimen with which I was favoured by Kiitzing, 

 I find the Naviculse 0'03 millim. long, and 0'0064 broad, 

 corresponding to the description of Kiitzing, and larger 

 than his figure (9-5 millim. ^ = 0'0226). 



I cannot understand why Kiitzing gives this form as a 

 variety of the preceding, whilst in external characters, in 

 the dimensions and the shape of the Naviculae, there are 

 distinctive appearances sufficient and comparable to those 

 by which other species are distinguished. 



Monnema cclocarpoides, Mgh. 

 Schizonema viride, Ktz. 



The enforcement of the law of priority is, without 



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