THE SPERMATOPHORE IN ARENICOLA LOLI 
ORIGIN OF THE SPERMATOGONIA 
Lillie says of A. cristata: 
.The early germ cells in connection with each nephridium become dis- 
tinguishable soon after the appearance of the blood vessel of the latter 
and arise as a proliferation of the peritoneal cells of its walls. They 
appear first on the anterior and first formed portion of the vessel, i.e., 
in the region immediately adjoining the posterior angle of the funnel. 
The germ cells usually appear on their respective nephridia i in the order 
of formation of these organs, 1.e., in order from before back. 
This peritoneum out of which the germ cells differentiate is 
derived from large teloblastic nuclei located at the posterior por- 
tion of the embryo in the growing zone, which nuclei Lillie thinks 
are the homologues of the definite teloblast cells found in such 
forms as Clepsine and Lumbricus. They in turn are apparently 
direct descendants of 4d, one of the fourth quartette of blasto- 
meres derived from the macromeres at the sixth cleavage, as 
described by Child. 
I have endeavored, in Arenicola, to discover some constant 
characters in the germ cells, which, appearing also in certain of 
the peritoneal cells, would enable me to trace the germ cells back 
through successive generations to the derivatives of 4d. But in 
this I have had no success and we must conclude that, as far as 
optical characters are concerned, the germ cells are indistinguish- 
able by present methods from the other peritoneal cells. In 
other words, the differentiation of the germ cells is probably called 
forth by stimulation of adjacent cells due to progressive inherent 
changes. 
Such a differentiation of the germ cells from the peritoneum is 
common in the annelida. ‘‘ Die Bildungstétten der Geschlechts- 
producte gehéren bei den Ringwiirmern genetisch den epithelialen 
Wandungen des Céloms an und erscheinen in Folge diesen als 
directe Abkommlinge der Mesodermstreifen oder des secundaren 
Mesoderms.”’ (EK. Meyer, Studien itiber den K6rperbau der 
Anneliden, 11.) 
JOURNAL OF MORPHOLOGY, VOL. 22, NO. 4 
