SEA-FISHERIES LABORATORY. 113 



The characteristic of this stage is the enormous develop- 

 ment of this reticulum, which has all the characters of a 

 tissue produced by the rapid multiplication of nuclei, 

 without a corresponding differentiation of cell bodies and 

 walls. In some sections the space occupied by it is so great, 

 that the appearance is almost that of a homogeneous 

 nucleated matrix, perforated in many places. 



The description given of this stage applies to the 

 Mussels obtained from the Wallasey and Morecambe 

 beds, the Roosebeck outer scar, and from those in the 

 Barrow Channel. Mussels obtained from the Roosebeck 

 inner scar have different characters in respect of the 

 condition of the gonads at this stage, and these are 

 probably correlated with the different conditions of nutri- 

 tion obtaining on this bed, which have been commented 

 on in a former Report.* Spawning in these Mussels 

 leaves the mantle lobes delicate and transparent. The 

 reticular tissue has the form of an attenuated network of 

 large mesh, and, in consequence of this, the remains of 

 the genital tubules are more easily seen, and a resting 

 stage is not so conspicuous. 



Stage II. (PL II., fig. 7; PL I., fig. 2).— The period 

 of rest which follows immediately after spawning, and 

 which is represented by Stage I., is of short duration, and 

 as early as the beginning of September the developing 

 gonads may be seen in the mantle. There can be no 

 doubt that, after spawning, many of the tubules break 

 down and disappear, but it seems quite clear that the 

 more important branches persist in the mantle through 

 the period represented by Stage I. Towards the end of 

 September ripening has commenced, and proliferation! 

 from the germinal epithelium is in progress. At any 



* A. Scott. "Mussels and Mussel Beds." Lane. Sea-Fish. Laby. Report 

 for 1895, pp. 21—32. 



