ZOOLOGY AND BOTANY, MICROSCOPY, ETC. L63 



Growth of Limpet's Shell.* — E. S. Russell has studied (1) the rate 

 of growth in the limpet's shell (taking the size of the shell as a measure 

 of its growth), and (2) the gradual change in the shape of the shell as 

 it grows in size. His conclusions are the following : 1. The breeding 

 season extends from July to January. 2. Sexual maturity is reached 

 at a length of 20-25 mm. 3. An average size for a limpet of the last 

 season's brood in January or February is 10 mm. At the end of the 

 first year it may be 29 mm. long. Probable sizes at the end of the 

 second and subsequent years are 38, 44, 48, and 53 mm. Shells over 

 50 mm. may be considerably more than five years old. 4. Sexual 

 maturity is reached in the first year, and when the limpet is only half- 

 grown. 5. The rate of growth decreases with age and maturity. It is 

 slower during the colder months of the year. 6. Considerable change 

 takes place in the ratios of the shell dimensions during growth. 7. 

 These changes are probably, in large part, the expression of " laws of 

 growth," and not due to natural selection. 



Hermaphroditism in Crepidula fomicata.f — J. H. Orton dis- 

 cusses this interesting Calyptrasid, which has been imported to England 

 from America along with oysters, and has established itself on the coast 

 of Essex and Lincolnshire. Individuals have the habit of associating 

 permanently in linear series, one on the top of another, forming " chains " 

 — sometimes of as many as twelve. All the young are able to creep 

 about, but the adults are sedentary. The individuals in a chain offer a 

 transitional series, from maleness to femaleness, both in primary and 

 secondary sexual characters. Since all the young ones are males, the 

 species is a protandrous hermaphrodite. Dwarf females occur as " physio- 

 logical variations.' 



Allied species and a species of an allied genus will very likely be 

 shown to be likewise protandrous, and there is good reason for thinking 

 that this condition may be even more widely spread among the Strepto- 

 neura. " Since the males in Crepidula fornicata change into females, it 

 would seem in this case that it is the male which possesses the potenti- 

 alities of both sexes. A solution to this problem is offered, if, as seems 

 likely, allied species present an evolutionary series in the acquisition of 

 protandric hermaphroditism." 



Classification and Distribution of Helicidae.ij: — H. von Ihering di- 

 vides the Helicidae into five new sub-families : — 1. Hygrorniinas (includ- 

 ing Hygromia Risso (Fruticicola Held), Eulota Hartm., Helicodonta Fer. 

 (Gonostoma Held), Lysinoe H. and A. Ad., Acanthiaula Beck, Vallonia 

 Risso. 2. Helicellina?, including Helicella Fer. (Xerophila Held.), and 

 Leucochroa Beck. 3. Cepolinae, including Gepolis Montf . and Polymita 

 Beck. 4. Heliocostylinee, including Helicostyla Fer. (Cochlostyla Fer.), 

 and Uhlorsea Alb. 5. Helicinse, including Helix (L.) Ih., Heliciyona Fer. 

 (Campyleea, Arianta, etc.), and Leptaxis Lowe. 



He discusses the Atlantis theory of Heer and his own Archhelmis 

 theory, and the probable migrations of HelicidaB in the past. Two " ele- 

 mentary laws of distribution" are formulated : — 1. Terrestrial animals, 



* Proc. Zool. Soc, 1909, pp. 235-53 (1 pi.). 



t Proc. Roy. Soc.B, lxxxi. (1909) pp. 468-84 (3 figs.). 



% Verb. Zool. Bot. Ges. Wien, lix. (1909) pp. 420-55 (1 map). 



