Dublin Microscopical Club. 417 



DUBLIN MICROSCOPICAL CLUB. 



June 24, 1880. 



Ttvo probably distinct forms of Penicillium. — Mr. Pirn showed 

 two forms of PenicilUum perhaps specifically distinct, one with the 

 chain of spores repeatedl)' branched, the other presenting only four 

 or fi.ve quite simple chains. They were the extreme forms, on either 

 side, of which P. glaucum may be looked upon as the mean. The 

 compound form occurred on a decaying Agaric, and the simple one 

 on dead flowers of Euphorbia jacquinueflora . 



TricJiodectes subrostratus. — This louse from a cat was shown by 

 Dr. W. M. A. Wright. Two of the specimens of this species (which 

 had not hitherto been found in Ireland) corresponded with the 

 description given by Denny ; the third had a bituberculate apex to its 

 rostrum, and so answered more closely to the species described by 

 Burmeister. 



Tivo rotund, granulate Staurastra, one referred to St. turgescens, De 

 Notaris, and another {^probably undescribed) superjicially resembling but 

 essentially distinct, anchuith distinct zygospores. — Mr. Archer exhibited 

 the zygospore of a Staurastrurn which, as regards the parent form 

 itself, seems to come very near that which he for the present identifies 

 as St. turgescens, De Notaris ; and to a casual observation indeed they 

 might seem identical. The form attributed to De Notaris is more 

 plump and rounded — seemingly in itself an inadequate difi'erence on 

 which to found a species ; but yet this seemed to carry with it internal 

 differences in the mode of arrangement of the contents. In the form of 

 which the zygospore was shown on the present occasion the mode of 

 arrangement of the contents in the parent form was strictly that of a 

 typical Staurastrurn, or that most common in the genus- — that is to 

 say, the contents forming pairs of chlorophyll plates radiating from 

 the central axis of each semicell towards the angles. This might 

 probably be called the medio-laminar arrangement, or, better, the 

 elasmo-mesenteric arrangement (that by far the most common in 

 Desmidieai), in contradistinction to the mode prevailing in certain 

 other species, where the chlorophyll lies in variously disposed and 

 specifically more or less characteristic plates on the interior of the 

 outer wall, which might be called the parieto-laminar arrangement, 

 or, better, the elasmo-pleurenteric arrangement. Now in the form 

 identified as St. turgescens, De Notaris, the mode of arrangement of 

 the contents is different; for the chlorophyll masses, though radiating 

 from the centre, do not form double lamina?, but irregular rays, 

 projecting in every direction ; they thus somewhat compare to the con- 

 figuration of the contents in the joint of a Zygnema. This might be 

 called the stellate arrangement, or, better, the astro-mesenteric ar- 

 rangement, and is rare in Desmidiese, but characteristic of the non- 

 constricted genus Cylindrocystis. But, above all, the form now 

 shown, however it may externally resemble that of De Notaris, dif- 



