Prof, M, Schultze on the Genus Cornuspira. 309 



This causes the objection by which the genus Cornuspira is to 

 be got rid of, to appear the more remarkable and incautious. 

 It is literally as follows : — " The small calcareous-shelled Planor' 

 iis-like forms which occur in many species, and not unfrequently 

 in the sea, I have recognized partly as small worm-shells 

 of Annulate worms, such as Serpula spirorbis; but they were 

 partly undoubted young states of Polythalamia of the most 

 different kinds. Of these young states of the larger Polytha- 

 lamia, which are abundant everywhere, Professor Max Schultze 

 has recently formed the new genus Cornuspira, although the 

 author himself says (p. 10) that the Agathistegia, in their earliest 

 youth, are not to be distinguished from his Cornuspirce, and he 

 has had no opportunity of observing a living animal. They 

 should therefore have been indicated with doubt as young Aga- 

 thistegia, and not as a new genus. But — they increased his 

 Monothalamia.'^ 



Ehrenberg therefore asserts that the Cornuspira are young 

 states of larger Polythalamia of the most different kinds. The 

 names of these kinds arc not mentioned, with the exception of 

 the Agathistegia, to which I had already directed attention, and 

 therefore must have had reasons for maintaining the distinction, 

 notwithstanding the affinity. As connected developmental series 

 of Polythalamia, to which we might refer in testing Ehrenberg's 

 assertion, are still very little known, we are driven, in inves- 

 tigating the question of the form of the young states of the 

 larger Polythalamia, to deduce this from the forms of the shells 

 in the mature animals, which may be effected with great cer- 

 tainty. My numerous observations of living young Polythala- 

 mia on the coasts of the Adriatic and in Heligoland, the study 

 of their gradual growth, together with numerous comparative 

 measurements of the shells of young and old individuals of 

 the same species, have led to the result that the form and size, 

 especially of the internal space of the youngest chambers, do 

 not subsequently change essentially, and that therefore every 

 Polythalamion at one time in its youth had the appearance 

 which will be found subsequently in its oldest, first chamber, or 

 the complex of several of them. This, indeed, does not require 

 to be specially proved; but it follows of itself, from the processes of 

 growth of the Polythalamia (for example, in a spiral Rotalide), that 

 we need only look at the form of the innermost, oldest chambers, 

 to know the form of the young state. In thick-shelled species 

 we resort to cutting. It is exactly the same as with a cham- 

 bered Nautilus-%\\e\\, or, not taking into consideration the dis- 

 sepiments, with any spiral shell. If therefore the Cornuspira 

 be the young of larger Polythalamia, the latter must exhibit a 

 commencement of shell-formation like a Cornuspira ; the centre 



