Notes on the morphology of the Tunicata. 537 



der Nervenknoten, der dem Ganglion des Geschlechtsthieres voll- 

 kommen gleicht; die Wimpergrube, die ganz ebenso ist, mündet in 

 die Pharyngealhöhle im dritten Intermuscularraum" — and then passes 

 on to another subject. He does not mention the neural gland; still 

 his previous reference to the metamorphosis of the tadpole, as well 

 as his figures (fig. 4, tab. 4; figs. 1 and 3, tab. 5; fig. 6, tab. 9 and 

 fig. 8, tab. 12) show that he has seen the neural gland in the nurse 

 form of DoUolum mulleri and D. ehrenhergi, and that, in both, it has 

 the same external appearance as in the sexual D. mulleri. 



I have had for study fourteen individuals of D. affine. They 

 have eight muscle bands and show no ventral stolon or dorsal 

 process and so cannot be "nurses". They have no trace of reproductive 

 organs. Thirteen of them show a slight projection arising on the mid- 

 ventral line, far back, near the lower edge of the atrial aperture. 

 This small process projects backward. It is evidently the remnant 

 of the stalk by which the individual was attached to the "nurse", for 

 in five of the specimens there are buds upon the stalk, evidently 

 the sexual buds. The presence of this miniature stalk and the absence 

 of reproductive organs show my specimens to be Phorozoids ("second 

 nurses" of Gkobben). In none of the fourteen individuals 

 examined have I found a trace of any neural gland. 



It is possible that the Phorozooid possesses a neural gland when 

 younger and loses it later by a process of degeneration such as aiîects 

 the viscera of the "nurse" in its later life and has been called by 

 Uljanin the metamorphosis of the "nurse". However, as all the other 

 organs of my specimens are normal and in good histological condition, 

 I think it much more probably true that the neural gland is wholly 

 wanting in the Phorozooids of Boliolum. 



The ciliated funnel (dorsal tubercle) is present in the usual place, 

 and a long, very slender duct leads back from it to the ganglion 

 (Fig. 57). 



One of my fourteen specimens has no postero-ventral stalk. It 

 is fully twice as long as the other specimens and is eight times their 

 bulk. It may be a sexual individual which has discharged its repro- 

 ductive products and in which the gonad has atrophied. This in- 

 dividual shows no neural gland, but, as in the other specimens, the 

 funnel is present and is joined to the brain by a very delicate duct. 



A rapheal nerve is present in Boliolum, but its fibres are not 

 associated with ganglion cells. The nerve arises from the posterior 

 end of the ganglion. 



