208 Miscellaneous. 
the above facts that the power of any part of an Actinospherium 
to develop into a perfect individual was inherent, and not depen- 
dent upon any peculiar condition of the animalcule. 
Fig. 8, pl. xli. of Leidy’s Rhizopods of North America, which he 
doubtfully refers to the Actinospheria, exactly resembles a medium 
stage in the development of the globules ejected from the body of 
the Actinospheria. 
The observer stated that the rays of <Actinospheriwm, when 
irritated by being compressed, would be retracted completely on all 
sides, and would again appear on the cessation of the disturbance. 
The length of time needed for the development of the <Actino- 
spheria, in the reproduction by natural means, was from seven to 
fourteen days ; that needed for the development in the reproduction 
by artificial means was from one to two days. 
In the latter case this length of time was needed only in cases 
when the crushing was carried to extremes, as when the Actino- 
spherium was simply divided into small pieces, a few hours were all 
that was needed to complete the development of the fragments.— 
Proc. Acad. Nat. Sct. Philad., June 5, 1883, p. 125. 
The * Crag Mollusca ”—Purpura tetragona. 
To the Editors of the * Annals and Magazine of Natural History. 
GentLemMEN,—In reference to the letter of Dr. Jeffreys, in your 
last number, wherein he says, “‘ in JJurew the canal is of moderate 
length, and is more or less covered over or closed above ; in Purpura 
the canal is very short and quite open,” I would mention that out 
of 113 specimens of the recent shell picked up on Felixstow beach, 
which I identify with Purpura tetragona and Murex erinaceus, 
61 have the canal wholly open, and 52 have it more or less covered 
over or closed above. These, though varying very much in size, 
appear from the number of whorls to be all adult shells, all sizes 
oceurring in either yroup. In the forms most approaching to the 
ordinary one of JZ. erinaceus (4. ¢. those most rugose and least 
elongate) the closing of the canal prevails; and the specimens with 
closed canal have usually the lip and varices most thickened. The 
specimens of Purpura tetragona which I have from the Felixstow 
Crag are all more or less mutilated, so that the length of the canal 
cannot be depended on; but in those I have from Walton Naze, 
and which are all in fine preservation, the canal is no shorter in 
proportion either to the length of the mouth or to the length of the 
shell than it is in Murea erinaceus. In its more elongated form, 
relative shortness of mouth, greater number of ribs or varices, and 
sharpness of shoulder, the variety alveolatus (fig. 76 of tab. iv. of 
the ‘Crag Mollusca’), which is almost the only one found in 
the oldest portion of the Red Crag (that of Walton), differs from the 
varieties found most abundantly in the rest of the Red Crag; and 
in these respects it departs more from the recent shell im question 
than do the latter. The varieties vulgaris, intermedia, and tenera 
