114 ANDREWS. [Vol. V. 



one or both cell strings is common, as in b, d, e. This branch- 

 ing is the rule in D. magna, while in D. cuprea it is rare. In 

 only one case observed, c, the strings of two ova were continu- 

 ous as in that figure. 



Regarding the cell arrangement in the branching of the strings 

 of D. magna, we may say that the usual method of division, with 

 planes at right angles to the length of the string, is sometimes 

 replaced by the occurrence of an oblique plane (Fig. 3, c) result- 

 ing in a side bud, or small cell, which, however, may be formed 

 as a marked lateral growth previous to division, as in f. When 

 this plane coincides with the long axis of the string, as at the tip 

 of e, a bifurcation probably results, such as is illustrated in b 

 and d, yet this may also be due to great growth of a side branch. 



However complex the branching of the cell strings of D. magna 

 may become, the egg finally, in a stage between /and g (Fig. 2), 

 gets rid of these appendages altogether, and completes its growth 

 as a simple, spherical cell, which is characterized superficially by 

 an area of greenish pigment surrounding a clearer protoplasmic 

 area on one side. This area coincides with the nucleus as to size, 

 but the latter is now no longer seen, since the egg has become 

 opaque owing to the accumulation of yolk granules. 



The actual dimensions of these floating eggs and cell strings 

 in D. magna are about as follows : the smallest measure 40 fi., 

 with a nucleus 20 /x. and nucleolus 6 /x. ; each appendage is now 

 380 /x. long, and 10 /x. and 20 /x. wide at the two ends, often con- 

 taining about 1 5 cells, exclusive of those in any small branches 

 that may be present. 



At this period little or no green pigment is perceptible. 

 When the egg has become 100 /x. in diameter, with a nucleus 

 50 /x. and nucleolus 13 fx., the appendage is about 430 /x., with 

 about 40 cells, having diameters of 30 fx. and 20 /x. at the two ends 

 of the series. The strings may become longer, but in most ova 

 about 500 /x. thick they seem to have shortened again, and finally 

 disappear in these 550/*., so that ripe ova measuring 600 \x. have 

 no trace of such appendages. 



The fate of the cell strings could not be determined, but some 

 observations indicate that they gradually disintegrate and fall 

 off, cases being observed in which only one or two cells were 

 left adhering to the ovum : yet these may have been, partly, at 

 least, pathological changes occurring in the sea-water, which, at 



