1. Meet Concretia Late Neurula stage (Optic bud formation) Stage: 18 26 hours old! --Kupffer’s vesicle is beginning to form and is enlarging. Anterior end of the keel has broadened into two divisions of the rudimentary brain. The embryonic axis about 1 mm in length and the mesodermis is reducing laterally. A solid optic bud (rudimentary eye vesicle) appears on each side. The beak-like cell mass is still visible. A small part of the yolk sphere still forms a blastophore at the vegetal pole, but is only a small opening.

2. Concretia Day 2 Not much of Concretia has changed. She is getting easier to see, and her structures more visible to us. By the next day we predict to be able to see a beating heart.

3. Day 3:Start of a HeartBeat! Stage: 23 46 Hours Old! Somite Stage There is a heartbeat! Around 59 beats per minute. The anterior portion of the straight-tubed heart reaches beneath the posterior end of the eye vesicle. A pair of semi-circular blood vessels and the vitello-caudal vein begin to form on the yolk sphere. Kupffer’s vesicles shrink. The neuro-coele is formed in the fore-, mid- and hind-brains. The spherical optic lenses are form completely. Around 15 somites are formed. A blood island becomes pronounced in the ventral region. The oil droplets have formed into a single large drop.

4. Day 8 144 hours old Stage: 33 Notochord Vacuolation Many internal organs haven’t been developed. The swim bladder now appears very small as a clear vesicle mesial to the urinary bladder. Her heartbeat increased to about 148 beats per minute. The eyeballs (choroidea) are very dark, and are cute. The notochord is completely vacuolized to the end of the tail. The pineal gland is distinct at the dorsal surface of the vascularized forebrain. The tips of the membranous margins of the pectoral fins reach the 4 th somite.

5. Day 9 168 hours old Stage 34 With careful observation of the region beneath the olfactory lobes, the lower jaw is seen to twitch very infrequently. There is a yellowish cast to the dorsal aspect of the head and trunk. The eye seems to be moving, but maybe not. Cornea has lifted well off the lens. The tail seems to be poling out and dorsal fin is present, but not as extensive as the ventral fin.

6. Day 10 200 hours old Stage 35 The spleen arises as a small crimson colored rudiment between the urinary and swim bladders. It’s color intensity and intial shape are variable. The live is seen. As the head flexure begins to straighten out, the mouth is moved upward and becomes visible in dorsal view. Golden chromatophores are scattered over the dorsal surface of the animal melanophores spot the head.

7. Day 11 264 hours old Stage 36! The swim bladder is about the size of the remaining oil globule. The urinary bladder and spleen may be brightly colored, and together with the liver, are located on the left side. The intestines passes between the 2 bladders. The caudal fin is rounded ad fin rays are forming within. The narrow dorsal fin extends ½ way to the head. The ventral fin will be remodeled into the anal fin. The swim bladder has inflated. All organ systems are represented in this stage, although many changed must happen before the adult structure is attained.