3312 Microscopical Society. 



large membranous segment succeeding the head having been considered by some an 

 thors as a portion of the head itself.* It is true, indeed, that this large segment is des- 

 titute of spiracles, and that the first pair of legs seems placed rather on the fold between 

 it and the following segment; that, moreover, the first pair of spiracles is placed in the 

 following segment, and, as it is the general principle of larvae to have the first pair of 

 spiracles either in the first, or in the fold between the first and second segments, it 

 might at first sight seem to warrant the conclusion that the large membranous seg- 

 ment following the head is really part of the head. But when the corneous head itse 

 is separately examined, it presents all the characters of a perfect head, and it is seei 

 moreover, that the second pair of legs is certainly attached to the segment which bears 

 the first pair of spiracles, we shall be compelled to consider the first segment as vr 

 duced to the small inferior fold which bears the first pair of legs. Taking all thes 

 circumstances into consideration, the President was clearly of opinion that the larg 

 segment in question is not part of the head, but is the real first segment greatly devt 

 loped ; and that the position of the first pair of spiracles on the second segment of th 

 body is anomalous. — J. W. D. 



Proceedings of the Microscopical Society of London. 



October 22, 1851. — A paper " On the Sporangia of some of the Filamentous Fresh- 

 water Algae," was read by Mr. George Shadbolt. 



This was in continuation of a subject introduced to the notice of the Society in 

 May last, by the same gentleman, when he pointed out the fact that in Zygnema quad- 

 ratum and Z. varians, the sporangia undergo a considerable change of form, assuming 

 a stellate character after the lapse of some weeks from their first transformation. The 

 second paper detailed observations confirming those previously announced, and giving 

 some of the particulars of the modus operandi, and added Lyngbya floccosa, and a spe- 

 cies of Vesiculifera to the list of those in which the author had noticed an analogous 

 transformation. 



It was stated that in Zygnema varians, after conjugation, when the sporangium 

 appears as an ellipsoidal homogeneous mass, the first change which takes place is the 

 formation of a few semi-transparent vesicles, just within the sporangium, and these 

 continually increase in number until the whole of the interior becomes similarly con- 

 verted. After the interval of about a fortnight from this period, a further change oc- 

 curs, the sporangia being covered with long projecting spines, producing a considerable 

 inflation of the original cell- wall of the frond in which they were formed, a fact which 

 the author considers important, as tending to prove the contined existence of vitality 

 in the cell at this stage. 



It was stated that in Lyngbya floccosa the spines are exceedingly short, but what 

 is remarkable, they are disposed in a regular spiral line about the long axis of the spo- 

 rangium. 



In Vesiculifera ? the spines are numerous and extraordinarily delicate. 



In all the above-named species, the observations were made while the sporangia 

 were still within the original frond, so that there is no doubt as to which each belonged. 

 — /. W. 



* See various papers in the ' Annales de la Socicte Entomologiqe de France.' 



