Miscellaneous. 187 



4. " On some Species of Acidaspis from the Lower Silurian beds 

 of the South of Scotland." By Professor Wyville Thomson. Com- 

 municated by J. W. Salter, Esq., F.G.S. 



The author described three new species of the trilobitic genus 

 Acidaspis, from the Lower Silurian flagstones with Graptolites and 

 Orthoceratites of Pinwhapple Glen, and one from the overlying 

 sandstone of Mullock Hill, Ayrshire. The names proposed for these 

 species were Acidaspis Lalage ; A. hystrix ; A. unica ; and the fourth, 

 ui. callipareos. 



5. " On two Silurian Species of Acidaspis from Shropshire." Bv 

 J. W. Salter, Esq., F.GS. 



In this communication Mr. Salter gave descriptions and figures 

 of Acidaspis coronata, sp. nov., from the Lower Ludlow Rock, and 

 A. Caractaci, from the Caradoc or Bala Sandstone of Gretton. The 

 latter species had been previously described, but not figured. 



MISCELLANEOUS. 



Observations on the Organization and Reproduction of the 

 Volvocinese. By F. Cohn. 



The author states that his observations on Volvox globator have 

 convinced him that its proper place is amongst the Algae. In it, as 

 in the Eudorince, Gonia, Stephanosphcera , and other VolvociriecB, 

 each spherule is not so much an individual properly so called, as an 

 association or family of individuals, — a sort of vegetable polypary. 

 A globe of Volvox is formed at its periphery by an infinity of very 

 small six-sided cells, soldered together like the elements of an epi- 

 dermic tissue. Each of these cells is furnished with two moveable 

 cilia, and may be compared to a Chlamydococeus ; its green endo- 

 chrome is as it were suspended in its cavity, and only touches its 

 walls by means of filiform processes. 



Like all Algae, Volvox possesses two modes of reproduction, but 

 hitherto only one of these has been known to naturalists : this con- 

 sists in a continual division of their cells, and recalls the scissiparity 

 of Chlamydococeus or Gonium, or that of most of the Pabnellacece. 

 In each sphere of Volvox there is never more than a very small 

 number of utricles, which are charged with this part of multiplica- 

 tion. By the continual binary division of their endochrome, these 

 special utricles, which are simple at first, come to contain as many as 

 12,000 distinct cells, and thus become so many new spheres, which 

 soon free themselves. 



The second mode of reproduction of the Volvox requires a sexual 

 concourse, and is not observed indifferently in all individuals. The 

 spherules endowed with sexuality are recognizable by their size and 

 by the greater number of their component utricles ; they are generally 

 monoecious, that is, they contain both male and female cells ; but 

 the greater part of their elements is neutral. The female cells soon 

 exceed their neighbours in size ; they acquire a deeper green tint, 

 and become elongated, in the manner of a matrass, towards the 



