94 



SUMMARY OF CURRENT RESEARCHES RELATING TO 



unites Monormia Berk, and Hormosiphon Kg., and distinguishes the 

 following groups and species. 



1. Intricata. Aquatic, softly gelatinous, without definite form, 

 often floating : — N. Hederulce Men., tenuissimum Ebh., Linkia Roth., 

 intricatum Men., crispulum Ebh., piscinale Kg., carneum Ag., rivulare 



Kg. 



2. Gelatinosa. Fixed ; soft and gelatinous. Cells of the young 

 filament elongated cylindrical. Sjiores large, elongated : — N. spongice- 

 forme Ag., gelatinosmn Shousboe, elUpsosponuii Rbh. 



8. Humifusa. Terrestrial. At first globular, afterwards coalescent 

 and gelatinous, forming coatings adherent to the substratum. Spores 

 smooth : — N. coUinum Kg., muscorum Ag. var. tenax Thur., Passerini- 

 anum De Not., Immifusum Carm., calcicola 'Breh., foliaceum Morg. 



4. Communia. Terrestrial, occasionally aquatic. At first globu- 

 lar, subsequently tongue-shaped, flat and irregular, not attached to 

 the substratum : — N. cimifiorum Tourn. (comimme Vauch.). 



5. Splicerica. Globular, or often irregularly round when they 

 grow larger. Surface firm and resistent : — N. sphcericum Vauch., 

 rupestre Kg., macrosporum Men., sphceroides Kg., cceruleum Lyngb,, 

 miniitissimum Kg., gregarmm Thur., edule Mont., and Berk., pruni- 

 forme Ag, 



6. Verrucosa. Aquatic; rounded or disk-shaped, at first solid, then 

 hollow, protected by a firm tough membrane. Filaments delicate, 

 distant, and somewhat curved in the middle, crowded and much bent 

 at the ends:— iV^. verriicosum Yanch., parmelioides Kg. 



7. Zefterstedtiana. Aquatic ; globular, hard, warty, divides 

 readily into separable segments : — N. Zetterstedtianum Aresch. 



8. Flagelliformia. Terrestrial ; narrow, linear, forming dichoto- 

 /mously divided bands : — N. flagelliforme Berk. 



Diatoms of Thames Mud.* — Dr. F. Bossey has investigated the 

 fresh- and salt-water diatoms found in mud-banks in the Thames, for 

 the purpose of showing the influence of the flood and ebb tides on their 

 formation, and gives the details of the result in an elaborate table. 



Mud taken from seven different localities showed the following 

 proportions of fresh-water and salt forms : — 



Half a mile above Teddington Lock 

 One mile below Teddiugton Lock .. 



Kew 



Blackwall 



Estuary of the Thames 



Dr. Bossey considers that in face of these facts the study of the 

 natural history of the Thames mud aflbrds important evidence in 

 support of the position taken up by the Conservators of the Thames, 

 that the mud-banks forming in the river owe their origin to the 

 discharge of matters from the outlets of the main-drainage system. 

 * Proc. Holmesrlale Nat. Hist. Club, 2 pp. and a table. 



