1876.] On the Development of the Crustacean Embryo. 375 



these disturbances more difficult to prove it on account of the close double 

 maximums which show variations from one year to another*. 



However, it is easy to see, in either of the figs. 4, 5, or 6, that the 

 dotted curves are generally displaced to the right of the plain. This 

 difference in behaviour between the easterly and westerly disturbances 

 still tends to support the supposition of their different sources. It is 

 very probable that these movements are periodical. 



The staff at the Observatory who can be engaged in measuring the 

 photographic curves of the magnetograph, and making the calculations 

 upon the monthly tables, is at present engaged with the curves of the 

 bifilar and balance magnetographs for the years 1868 to 1871. 



It would be very interesting to know if similar displacements in the 

 disturbance-curves at the stations in Asia and America have been ob- 

 served, and in what direction. 



The following Table gives the total of the disturbances of the decli- 

 nation : — 



West. East. East and West. 



millims. millims. millims. 



1864 1666-3 1797-4 3463-7 



1865 1970-6 1598-4 3569-0 



1866 1313-4 1382-6 2696-0 



1867 832-1 1164-5 1996-6 



1868 1635-0 1514-7 3149-7 



1869 1784-9 1755-8 3540-7 



1870 2486-0 1813-3 4299-3 



1871 2045-4 1734-1 3779-5 



13733-7 12760-8 26494-5 



Thus near 1870, or a little after, there is a maximum period of 

 disturbances, and from 1866 to 1867 there is a minimum period of 

 disturbances, agreeing with the observed periods for the maximum and 

 minimum of sun-spots. 



II. u On the Development of the Crustacean Embryo, and the 

 Variations of form exhibited in the Larvae of 38 Genera of 

 Podophthalmia." By C. Spence Bate, F.R.S. Received 

 December 28, 1875. 



(Abstract.) 



The author states that, although the general forms of several genera 

 of Podophthalmous Crustacea are known, yet the details of their struc- 

 ture have been so unsatisfactorily figured and described, that the value 



* It is observed that the hollow between the two maximums about noon corresponds 

 closely to another secondary maximum of the easterly disturbances. It thus appears 

 that, during the hours 20 a.m. to 3 p.m., there is another force in action independent 

 of the two principal forces. 



