344 Mr. G. H. K. Thwaites on Conjugation in the Diatomacese. 



all the others in one sporangium only, instead of two, being pro- 

 duced from the pair of conjugated frustules. This sporangium, 

 which is at first cylindrical, soon assumes a flattened somewhat 

 quadrangular form, and in many, but not in all cases, undergoes 

 fissiparous division before it has put on the exact appearance of a 

 frustule of the Fragilaria. 



It cannot be doubted that in a physiological point of view the 

 phenomena here brought forward are of great value, and there 

 are many questions relating to impregnation in plants and ani- 

 mals upon which they may have an important bearing. I pur- 

 pose in an early communication sending some observations on this 

 subject for insertion in your valuable periodical. 



I am, Gentlemen, your very obedient servant, 



G. H. K. Thwaites. 



P.S. October 23, 1847. My valued correspondent, the Rev. 

 William Smith of Wareham, has recently sent me specimens of a 

 new and very beautiful species of Schizonema (which I purpose 

 figuring and describing under the name of S. subcoharens), some 

 of the frustules of which I was fortunate enough to detect in a 

 conjugated state : the sporangia are produced in a similar way to 

 those of Cocconema. I am indebted to the same gentleman for 

 the opportunity of discovering the conjugated frustules of Eunolia 

 zebra, Ehr. (which a good deal resemble those of E. turgida), 

 Epit hernia gibba, Kiitz., and Fragilaria pectinalis, sent amongst 

 other interesting Algse from his neighbourhood. 



EXPLANATION OF PLATE XXII. 



Fig. A. 1. Filament of Fragilaria pectinalis, Lyng. : *, side view of frustule. 



— 2 to 5 inclusive. The same species in conjugation, exhibiting the 



sporangium in various stages of development. 



— 6 and 7. Mature sporangia of Fragilaria pectinalis. 

 Fig. B. 1. Frustules of Gomphonema minutissimum, Ag. 



— 2, 3 and 4. The same species in conjugation. 



— 5. Mature sporangia, become stalked like the frustules. 

 Fig. C. I. Cocconema lanceolatum, Ehr. 



— 2 and 3. The same in conjugation. 

 Fig.D. 1. Gomphonema, n. s . ? 



— 2 and 3. Different views of the same in conjugation. 

 Fig. E. 1. Cocconema Cistula, Ehr. 



— 2. The same species in conjugation. 

 Fig. F. 1 . Epithemia gibba, Kiitzing. 



— 2. The same in conjugation. 



